XXIV Conference on Dynamics of Molecular Collisions

July 7th - 12th, 2013

Granlibakken

Hua Guo, Chair

Arthur Suits, Vice Chair Granlibakken Resort Room Number Telephone Number

Gatekeepers& Steinbach Indian Basket T , MuseumS

Nordic Trails

Begin Par Course

Ski Lift

Ski Hill History of DMC

1. 1965 New Hampton, New Hampshire, John Fenn (Yale University) 2. 1968 Andover, New Hampshire, John C. Polanyi (University of Toronto) 3. 1970 Oak Ridge, Tennessee, E.F. Green (Brown University) 4. 1972 Plymouth, New Hampshire, Sheldon Datz (Oak Ridge National Laboratory) 5. 1974 Santa Cruz, California, James L. Kinsey (Massachusetts Institute of Technology) 6. 1976 Plymouth, New Hampshire, Bruce E. Mahan (University of California, Berkeley) 7. 1978 Pacific Grove, California, Yuan T. Lee (University of California, Berkeley) 8. 1981 Plymouth, New Hampshire, R. James Cross (Yale University) 9. 1983 Gull Lake, Minnesota, W. Ronald Gentry (University of Minnesota) 10. 1985 Snowbird, Utah, Donald G. Truhlar (University of Minnesota) 11. 1987 Wheeling, West Virginia, Paul Dagdigian (The Johns Hopkins University) 12. 1989 Pacific Grove, California, William H. Miller (University of California, Berkeley) 13. 1991 Lake George, New York, James M. Farrar (University of Rochester) 14. 1993 Helen, Georgia, Joel M. Bowman, (Emory University) 15. 1995 Pacific Grove, California, Daniel Neumark (University of California, Berkeley) 16. 1997 Gull Lake, Minnesota, George Schatz (Northwestern University) 17. 1999 Lake Harmony, Pennsylvania, James Valentini (Columbia University) 18. 2001 Copper Mountain, Colorado, James T. Muckerman (Brookhaven National Laboratory) 19. 2003 Tahoe City, California, Laurie J. Butler (University of Chicago) 20. 2005 Pacific Grove, California, Albert Wagner (Argonne National Laboratory) 21. 2007 Sante Fe, New Mexico, David Chandler (Sandia National Laboratories) 22. 2009 Snowbird, Utah, Anne McCoy (Ohio State University) 23. 2011 Snowbird, Utah, David Nesbitt (JILA/University of Colorado) 24. 2013 Granlibakken, California, Hua Guo (University of New Mexico) Dynamics of Molecular Collisions 2013 Schedule

Sunday, July 7

Arrival and Registration

4:00 - 6:00 pm, Registration, Mountain-Lake Room 6:00 - 7:30 pm, Dinner, Garden Deck 7:30 - 10:00 pm, Reception, Garden Deck

Monday, July 8

7:30 - 8:30: Breakfast, Granhall

Bimolecular Reactions I, Mountain-Lake Room

8:30 - 8:45: Session Overview: Kopin Liu (Academia Sinica) 8:45 - 9:15: David Clary (U. Oxford), Combining Quantum Dynamics and Quantum Chemistry for Reactions of Polyatomic Molecules 9:15 - 9:25: Discussion 9:25 - 9:55: Xueming Yang (Dalian Institute of Chemical Physics), Reagent Vibrational Excitation Effect on the Dynamics of the F+HD Reaction 9:55 - 10:05: Discussion 10:05 - 10:50: Coffee break 10:50 - 11:20: Tim Minton (Montana State U.) , Electronic Excitation in Hyperthermal Atomic Oxygen Reactions 11:20 - 11:30: Discussion 11:30 - 11:45: Contributing talk: Baptiste Joalland (Wayne State U.), Crossed-beam Slice Imaging of Cl Reaction Dynamics with Butene Isomers 11:45 - 11:50: Discussion 11:50 - 12:20: ZhigangSun (Dalian Institute of Chemical Physics), State-to-state Reactive Scattering by MCTDH Method 12:20 - 12:30: Discussion

12:30 - 2:00: Lunch, Garden Deck 2:00 - 4:30: Free (set up posters, odd numbers) 4:30 - 5:30: Poster Session (odd numbers), Bay Room 5:30 - 7:00: Dinner, Garden Deck

Non-adiabatic Dynamics, Mountain-Lake Room

7:00 - 7:15: Session Overview, SpiridoulaMatsika (Temple U.) 7:15 - 7:45: David Yarkony (Johns Hopkins U.), Electronic Structure Aspects of Nonadiabatic Dynamics: Reaction Mechanisms and Representations of Coupled Adiabatic States 7:45 - 7:55: Discussion 7:55 - 8:25: John Tully (Yale U.), Chemical Dynamics at Metal Surfaces: The Role of Electronic Excitations 8:25 - 8:35: Discussion 8:35 - 8:50: Break 8:50 - 9:05: Contributing talk, J. Jankunas (Stanford U.), Simultaneous Measurement of Reactive and Inelastic Scattering of H + HD ^ HD(v', j') + H Reaction: In Search for Geometric Phase Effects 9:05 - 9:10: Discussion 9:10 - 9:40: Anna Krylov (U. Southern California), On the Photodetachment from the Green Fluorescent Protein Chromophore 9:40 - 9:50: Discussion 9:50 - 12:00: Poster session (odd numbers), Bay Room

Tuesday, July 9

7:30 - 8:30: Breakfast, Granhall

Unimolecular Reactions, Mountain-Lake Room

8:30 - 8:45: Session Overview: Wen Li (Wayne State U.) 8:45 - 9:15: Don Truhlar (U. Minnesota), Photochemistry in Terms of Diabatic States 9:15 - 9:25: Discussion 9:25 - 9:55: Dan Neumark (U. California Berkeley), Probing Chemical Dynamics with Negative Ions 9:55 - 10:05: Discussion 10:05 - 10:50: Coffee break 10:50 - 11:20: Andrei Sanov (U. Arizona), Radical and Diradical Reactive Intermediates via Anion Photoelectron Imaging 11:20 - 11:30: Discussion 11:30 - 11:45: Contributing talk: Michael Lucas (U. California Riverside), Ultraviolet Photodissociation Dynamics of the Cyclohexyl Radical 11:45 - 11:50: Discussion 11:50 - 12:20: Bob Continetti (U. California San Diego), Studies of Neutral Reaction Dynamics using Dissociative Photodetachment: HCO2 and F + H2O ^ HF + OH 12:20 - 12:30: Discussion

12:30 - 2:00: Lunch, Garden Deck 2:00 - 4:30: Free 4:30 - 5:30: Poster Session (odd numbers), Bay Room 5:30 - 7:00: Dinner, Garden Deck

Cold Collisions, Mountain-Lake Room

7:00 - 7:15: Session Overview: Stefan Willitsch (U. Basel) 7:15 - 7:45: PascalHonvault (U. Franche-Comte), Quantum Reaction Dynamics Studies of Astrophysical Interest below 100 K 7:45 - 7:55: Discussion 7:55 - 8:25: Bas van de Meerakker (Radboud U.), Controlling Collisions using Stark- decelerated Molecular Beams 8:25 - 8:35: Discussion 8:35 - 8:50: Break 8:50 - 9:05: Contributing talk, Heather Lewandowski (JILA), Travelling-Wave Deceleration of Buffer-Gas Beams of CH 9:05 - 9:10: Discussion 9:10 - 9:40: Jeremy Hutson (Durham U.) Ultracold Hydrogen Atoms: A Versatile Coolant for Producing Microkelvin Molecules 9:40 - 9:50: Discussion 9:50 - 12:00: Poster session (odd numbers)

Wednesday, July 10

7:30 - 8:30: Breakfast, Granhall

Interface Dynamics, Mountain-Lake Room

8:30 - 8:45: Session Overview: Rainer Beck (EPF Lausanne) 8:45 - 9:15: David Nesbitt (JILA/U. Colorado), Probing Gas-Liquid and Gas-SAM Interfaces with Quantum State Resolved Collision Dynamics 9:15 - 9:25: Discussion 9:25 - 9:55: Bret Jackson (U. Mass. Amherst), Dynamics of Methane Dissociation on Ni and Pt Surfaces 9:55 - 10:05: Discussion 10:05 - 10:50: Coffee break 10:50 - 11:20: Alec Wodtke (U. Gottingen/MPI), Charge Transfer Reactions Induce Born- Oppenheimer Breakdown in Surface Chemistry: Applications of Double Resonance Spectroscopy in Molecule-surface Scattering 11:20 - 11:30: Discussion 11:30 - 11:45: Contributing talk: Bin Jiang (U. New Mexico), Mode/Bond Selectivity in Methane Dissociative Chemisorption on Ni(111) 11:45 - 11:50: Discussion 11:50 - 12:20: Geert-Jan Kroes (Leiden U.), Towards a Chemically Accurate Description of Reactive Molecule-surface Scattering 12:20 - 12:30: Discussion

12:30 - 2:00: Lunch, Garden Deck 2:00 - 4:30: Free (set up posters, even numbers), Bay Room 4:30 - 5:30: Poster Session (even numbers), Bay Room 5:30 - 7:00: Dinner, Garden Deck Bimolecular Reactions II, Mountain-Lake Room

7:00 - 7:15: Session Overview: Al Wagner (Argonne National Lab) 7:15 - 7:45: Bill Hase (Texas Tech U.), Simulations of X- + CH3Y Ion-Molecule Reactions. Roles of Non-Statistical Dynamics, Multiple Reaction Pathways, and Microsolvation 7:45 - 7:55: Discussion 7:55 - 8:25: Arthur Suits (Wayne State U.), Rydberg Tagging of Spin-Polarized Hydrogen Atoms 8:25 - 8:35: Discussion 8:35 - 8:50: Break 8:50 - 9:05: Contributing talk, Gabor Czako (Eotvos U.) Dynamics of Bimolecular Polyatomic Reactions on Ab Initio Potential Energy Surfaces 9:05 - 9:10: Discussion 9:10 - 9:40: Uwe Manthe (U. Bielefeld), Quantum Dynamics of Methane-Atom Reactions 9:40 - 9:50: Discussion 9:50 - 12:00: Poster session (even numbers), Bay Room

Thursday, July 11

7:30 - 8:30: Breakfast, Granhall

Clusters and Solution Reactions, Mountain-Lake Room

8:30 - 8:45: Session Overview: Marsha Lester (U. Pennsylvania) 8:45 - 9:15: Andrew Orr-Ewing (U. Bristol), Vibrationally Resolved Dynamics and Energy Flow for Reactions in Solution 9:15 - 9:25: Discussion 9:25 - 9:55: P.-N. Roy (U. Waterloo), Dynamics of Quantum Rotors in Complex Environments 9:55 - 10:05: Discussion 10:05 - 10:50: Coffee break 10:50 - 11:20: Fleming Crim (U. Wisconsin Madison) Dissociation and Isomerization in Clusters and Solution 11:20 - 11:30: Discussion 11:30 - 11:45: Contributing talk: Diane Lancaster (U. Wisconsin Madison), Inert Gas Scattering from Liquid Hydrocarbon Microjets 11:45 - 11:50: Discussion 11:50 - 12:20: Tim Zwier (Purdue U.) Multiple Resonance Methods for Conformation-Specific Spectroscopy and Dynamics 12:20 - 12:30: Discussion

12:30 - 2:00: Lunch, Garden Deck 2:00 - 4:30: Free 4:30 - 5:30: Poster Session (even numbers), Bay Room 5:30 - 7:00: Dinner, Garden Deck Award Session, Mountain-Lake Room

7:00 - 7:10: Introduction: Dave Chandler (Sandia National Lab), Arthur Suits (Wayne State U.) and HuaGuo (U. New Mexico) 7:10 - 7:50: Giacinto Scoles (U. Udine), Chemical Dynamics of Complex Reactions with Bio­ molecules: the Case of Restriction Enzymes in Highly Packed DNA Brushes 7:50 - 8:00: Discussion 8:00 - 8:40 Peter Toennies (MPI Gottingen), TBA 8:40 - 8:50: Discussion 8:50 - 9:30: Joel Bowman (Emory U.), Potential Energy Surfaces 9:30 - 9:40: Discussion 9:40 - 12:00: Poster session (even numbers), Bay Room

Friday, July 12

7:30 - 8:30: Breakfast, Granhall

Atmospheric, Astrochemical, and Combustion Reactions, Mountain-Lake Room

8:30 - 8:45: Session Overview: Richard Dawes (Missouri U. Sci. Tech.) 8:45 - 9:15: Ralf Kaiser (U. Hawaii Manoa), On the Formation of Interstellar Organo Silicon Molecules 9:15 - 9:25: Discussion 9:25 - 9:55: Hanna Reisler (U. Southern California), Imaging Bond Breaking in Hydrogen- bonded Dimers and Trimers 9:55 - 10:05: Discussion 10:05 - 10:50: Coffee break 10:50 - 11:20: David Osborn (Sandia National Lab) Isomers and Isomerizations in Tropospheric Chemistry: Opening the Black Box of Criegee Intermediate Reactions 11:20 - 11:30: Discussion 11:30 - 11:45: Contributing talk: Julia Lehman (U. Pennsylvania), Photodissociation Dynamics the Simplest Criegee Intermediate CH2OO and its Laboratory Precursor CH2I2 11:45 - 11:50: Discussion 11:50 - 12:20: Kristie Boering (U. California Berkeley) Reaction Dynamics and Kinetics of Oxygen Isotope Exchange Reactions: Insights into Unusual Isotope Effects and Their Applications in Earth and Planetary Science 12:20 - 12:30: Discussion 12:30 - 1:30: Lunch, Garden Deck

1:30: Conference adjourns Combining quantum dynamics and quantum chemistry for reactions of polyatomic molecules

David C. Clary

Department of Physical and Theoretical Chemistry University of Oxford SouthParks Road Oxford OX1 3QZ, UK

email: [email protected]

This lecture will describe research in our group on linking quantum dynamics and quantum chemistry methods to predict the kinetics and dynamics of reactions of polyatomic molecules from first principles. A reduced dimensionality approach is used that combines accurate quantum chemistry calculations of a small number of key on the potential energy surface with a quantum- dynamical treatment of the bonds being broken and formed in a chemical reaction. Applications to reactions such as H + butane, CHF3 and spin-orbit effects in the reaction Cl + CH4 will be described as will recent computational developments in the method. The calculations were performed by Xiao Shan, Sarah Remmert, Frank von Horsten and Simon Banks.

O1 Reagent Vibrational Excitation Effect on the Dynamics of the F+HD Reaction

Xueming Yang

State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China

In the recent years, we have made considerable progresses in the study of the dynamics of the benchmark F+H2 reaction using quantum-state resolved crossed molecular beams scattering method, in combination with accurate quantum dynamics theory. Experimental evidence of reaction resonances, HF(v=2) forward scattering, has been detected in a full quantum state resolved reactive scattering study of the F+H2(v=0) reaction. Highly accurate full quantum scattering theoretical modeling shows that the reaction resonance is caused by two reaction resonance states. This study is a significant step forward in our understanding of dynamical resonances in the benchmark F+H2 system. In addition, we have also studied the F+HD(v=0) system, this isotope substitution provided an extremely sensitive probe to the reaction resonance potential surface in this system. Further, we have also detected clearly partial wave resolved resonances in the F+HD reaction for the first time. Recently, we have developed an experimental scheme for highly efficient pumping of HD(v=1) from HD(v=0) using the stimulated Raman adiabatic passage (SARP) technique. And we have applied this technique to invesitgate the HD reagent vibrational excitation effect on the F+HD reaction. From the state resolved scattering experiment using the D-atom Rydberg tagging technique, we have found that the main reaction product from that F+HD(v=1) reaction is that HF in the v=3 state rather than the v=2 state from the F+HD(v=0) reaction. This indicates that the reaction is nearly vibrationally adiabatic, in which all excess vibrational energy is deposited to the HF product vibration. State resolved differential cross sections have also been measured, in good agreement with exact quantum calculations based on a newly constructed potential energy surface. Reaction resonances have also been observed in the experiment. A clear resonance picture is also obtained for this F+HD(v=1)^HF+D reaction using the quantum scattering dynamics method.

O2 Electronic Excitation in Hyperthermal Atomic Oxygen Reactions

Timothy K. Minton

Department of Chemistry and Biochemistry Montana State University Bozeman, Montana 59717 USA [email protected]

The high velocities of space vehicles that penetrate the atmosphere of the Earth lead to hyperthermal collisions between atmospheric constituents and the vehicles ’ surfaces, exhaust gases, and ablation products. For example, hyperthermal collisions in the vicinity of a spacecraft in Earth’s outer atmosphere typically involve atomic oxygen with relative velocities of 8 km s-1, corresponding to center-of-mass collision energies of many electron volts (hundreds of kJ mol-1). These high-energy collisions can result in reaction pathways and energy transfer processes that are unknown in terrestrial environments. The desire to understand hyperthermal collisions has motivated a number of studies of gas-surface and gas-phase inelastic and reactive scattering dynamics, employing a combination of molecular beam experiments and theoretical calculations. This presentation will feature the hyperthermal gas-phase reaction of atomic oxygen with acetylene and its deuterated analogue, O( P) + HCCH/DCCD ^ HCCO/DCCO + H/D. With collision energies of 40-150 kcal mol-1, this reaction may follow multiple pathways to form the ketenyl radical (HCCO or DCCO) in ground doublet states or in electronically excited quartet and doublet states. The fraction of electronic excitation is substantial. At a collision energy of 102 kcal mol-1, ~65% of the ketenyl radical products that survive are electronically excited, with the majority of the excited products in a quartet state. In this case, a population inversion exists between the electronically excited quartet and ground doublet states of the ketenyl product. Such significant electronic excitation in products is unusual in bimolecular reactions, especially when ground-state products are accessible by spin-allowed pathways. New results will also be presented on a similar hyperthermal reaction, O(3P) + H2S/D2S ^ HSO/DSO + H/D, whose product (HSO or DSO) can be formed in an electronically excited doublet state. This reaction was carried out in the c.m. collision energy range, 56-120 kcal mol-1. With a collision energy of 106 kcal mol-1, nascent DSO/HSO can undergo substantial secondary dissociation to SO + D/H. The surviving DSO/HSO (~57%) is formed in an electronically excited doublet state (2A').

O3 Crossed-beam Slice Imaging of Cl Reaction Dynamics with Butene Isomers

Baptiste Joalland, Yuanyuan Shi, Rick D.Van Camp, Nitin Patel, and Arthur G. Suits

Department of Chemistry, Wayne State University, Detroit, MI 48202

We present a crossed-beam imaging study of the reaction of chlorine atoms with several butene isomers. A high-intensity pulsed ablation Cl source is used with DC slice imaging and single-photon ionization detection at 157nm to record the velocity-flux contour maps for these reactions. The target unsaturated hydrocarbons are 1 -butene, trans-2-butene, cis-2-butene, and isobutene (2-methylpropene). Data are obtained at collision energies of ~13.0 kcal.mol-1. Distinct differences in the scattering distributions and in particular the coupling of angular and translational energy release provide insight into the dynamics of this little-studied class of reactions. We find that these distributions reflect the energetics for competition between addition/elimination and direct abstraction in line with ab initio thermochemical data. A possible role for Cl atom roaming mediating the addition/elimination pathway is suggested.

Fig1. DC sliced images of C4H7 products for 1-butene and isobutene reactions, with the Newton diagrams superimposed.

O4 State-to-state Reactive Scattering by MCTDH Method

Zhigang Sun

State Key Laboratory of Molecular Reaction Dynamics & Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China [email protected] http: //www.chemdyn.dicp.ac.cn/

In this report, new development on efficient state-to-state (SS) triatomic reactive scattering using quantum wavepaket method in our group will be introduced, using MCTDH method, basing upon our recently developed reactant coordinate based method[1,2,3,4]. Using MCTDH method, now we can extract state-to-state DCS of triatomic reactive scattering and further development is ongoing[5] . The merits and disadvantages of this method will be discussed.

Reference: 1) A Reactant-Coordinate-Based Time-Dependent Wave Packet Method for Triatomic State-to- State Reaction Dynamics: Application to the H + O2 Reaction, Zhigang Sun, D. H. Zhang, Soo- Y. Lee, J. Phys. Chem. A 113 (2009) 4145 2) Comparison of Second-order Split Operator and Chebyshev Propagator in Wave Packet Based State-to-state Reactive Scattering Calculations, Zhigang Sun, S.-Y. Lee, H. Guo, D. H. Zhang, J. Chem. Phys. 130 (2009) 174102 3) Extraction of state-to-state reactive scattering attributes from wave packet in reactant Jacobi coordinates, Zhigang Sun, H. Guo, D. H. Zhang, J. Chem. Phys. 132 (2010) 084112 4) Propagators for Solving Schrodinger Equation by Wave Packet Based Method: Application of Higher Order Operator Splitting Schemes to Triatomic Reactive Scattering Calculations, Zhigang Sun, Weitao Yang, D. H. Zhang, Phys. Chem. Chem. Phys. 14 (2012) 1827 5) State-to-state reactive scattering differential cross section by MCTDH method, Bin Zhao, Zhigang Sun, J. Chem. Phys. (To Be Submitted)

O5 Electronic Structure Aspects of Nonadiabatic Dynamics: Reaction Mechanisms and Representations of Coupled Adiabatic States

Joseph Dillon, Xiaolei Zhu and David Yarkony

Department of Chemistry, Johns Hopkins University

The mechanism of nonadiabatic processes and the quasi diabatic representations of adiabatic potential energy surfaces coupled by conical intersections will be discussed. The reactions

OH(A)+H2 ^ OH(X)+H2 , H2O + H

and

C6 H5 OH + hv ^ C6 H5 OH(S1, S2) ^C6 H5 O(X,A) +H will be considered.

The method for constructing quasi-diabatic representations of coupled adiabatic potential energy surfaces will be discussed, with emphasis on its ability to describe seams of conical intersection, and its extension from 4-5 atom systems to systems as large as phenol.

O6 Chemical Dynamics at Metal Surfaces: The Role of Electronic Excitations

John Tully

Yale University

The adiabatic (Born-Oppenheimer) approximation underlies most of our understanding of chemical reaction dynamics. It has become clear, however, that nonadiabatic electronic transitions can sometimes play an important role, particularly in photo-initiated and highly energetic reactions. It is not as widely known that for reactions at metal surfaces, even at thermal energies, nonadiabatic behavior is the rule rather than the exception. Electron-hole pair transitions, charge transfer and hot-electron-induced motion can be dominant pathways for energy flow and can drastically alter reaction pathways. Recent experiments have demonstrated that molecular vibrational energy and reaction exothermicity can produce highly excited electrons, even resulting in electron emission. This talk will present progress toward a unified picture of nonadiabatic dynamics at metal surfaces, with application to multi-quantum vibrational-to-electronic energy transfer in the scattering of nitric oxide from a gold surface.

O7 Simultaneous Measurement of Reactive and Inelastic Scattering of H + HD ^ HD(v', j') + H Reaction: In Search for Geometric Phase Effects

J. Jankunas,1 M. Sneha,1 R. N. Zare,1 F. Bouakline,2 and S. C. Althorpe 3

1 Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA

2 Max Born Institute, Max Born Strasse 2a, 12489 Berlin, Germany

3 Department of Chemistry. University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK

The H + HD ^ HD(v', jr) + H reaction has been studied experimentally and theoretically. Differential cross sections (DCSs) of HD(v', j') products have been measured by means of a Photoloc technique and calculated using a time-independent quantum mechanical theory. Three product states: HD(v' = 1, j' = 8) at a collision energy (Ecoll) of 1.97 eV; HD(v' = 2, j' = 3) at Ecoll = 1.46 eV; and HD(v' = 2, j' = 5) at Ecoll = 1.44 eV, show very good agreement between theory and experiment. The other two, highly rotationally excited states studied, HD(v' = 1, j'= 12) and HD(v' = 1, j' = 13) at Ecoll = 1.97 eV, exhibit a noticeable disagreement between experiment and theory. This is consistent with our most recent findings on the H + D2 ^ HD(v', j') + D reaction, wherein the differential cross sections of HD(v' = 1, high j') product states showed similar disagreement between the experiment and theory. In all five cases, however, we find overwhelming support that the experimental signal is a sum of reactive and inelastic scattering events. This work constitutes a first experimental example in which the indistinguishability of reactive and inelastic channels must be taken into account explicitly when constructing DCSs. An additional 30-day effort has been undertaken by collecting nearly 45000 ions in search of geometric phase effects in the H + HD ^ HD(v' = 2, j' = 5) + H reaction. The experimentally measured DCS for HD(v' = 2, j' = 5) product state has been fit to theoretical calculations that included the geometric phase and to those that did not. Although the experimental data cluster closely about the two theoretical DCSs, the difference between the two fits has been found to be statistically insignificant.

J. Jankunas, M. Sneha, R. N. Zare, F. Bouakline and S. C. Althorpe, “DisagreementBetween Theory and Experiment Grows with Increasing Rotational Excitation of HD(v', j') Product for the H + D2 Reaction”, J. Chem. Phys. 138, 094310 (2013). J. Jankunas, M. Sneha, R. N. Zare, F. Bouakline, and S. C. Althorpe, “Simultaneous Measurement of Reactive and Inelastic Scattering: Differential Cross Section of the H + HD ^ HD(v', j') + HReaction”, Z. Phys. Chem. (in press).

O8 On the photodetachment from the Green Fluorescent Protein chromophore

Anna I. Krylov

Department of Chemistry, University of Southern California, Los Angeles, CA 90089

Motivated by the discrepancies in recent experimental and theoretical studies of photodetachment from isolated model chromophores of the green fluorescent pro- tein (GFP), this study reports calculations of the electron detachment energies and photoelectron spectra of the phenolate and deprotonated p-hydroxybenzylidene-2,3- dimethylimidazolinone (HBDI) anions. The spectra were computed using double- harmonic parallel normal mode approximation. High-level coupled-cluster methods as well as density functional theory were used to compute vertical and adiabatic detachment energies of the phenolate anion serving as a model system representing anionic GFP-like chromophores (HBDI). The benchmark calculations reveal that the basis set has significant effect on the computed detachment energies, whereas the results are less sensitive to the level of electron correlation treatment. At least aug-cc-pVTZ basis set is required. The best roB97X-D and CCSD(T) estimates of phenolate’s adiabatic detachment energy are 2.12 and 2.19 eV; these values are very close to the experimental value, 2.253 eV [Gunion et al., Int. J. Mass Spectrom. Ion Proc. 117, 601 (1992)]. The best estimate of the vertical detachment energy of deprotonated HBDI is 2.76 eV, which supports bound character of the bright excited state in the Franck-Condon region. The most intense transition in the com­ puted photoelectron spectra of both phenolate and deprotonated HBDI is the 0-0 S0-D0 transition, which is 0.11 eV below vertical detachment energy. Therefore, the position of the maximum of the photoelectron spectrum does not represent vertical detachment energy and the direct comparison between theory and experiment must involve spectrum modeling.

O9 Photochemistry in Terms of Diabatic States

Xuefei Xu, Ke R. Yang, Osanna Tishchenko, Jingjing Zheng, Ruben Meana-Paneda, and Don Truhlar University of Minnesota

Ahren Jasper and Eugene Kamarchik Sandia National Laboratories

Bina Fu Dalian Institute of Chemical Physics

Joel M. Bowman Emory University

Rosendo Valero University of Coimbra

Michael W. Schmidt and Mark S. Gordon Iowa State University

The theoretical treatment of electronically nonadiabatic processes, both in bimolecular collisions of electronically excited species and in photodissociation, involves many challenges beyond those encountered in electronically adiabatic ones. There are two steps: (1) obtaining the potential energy surfaces and their couplings, (2) carrying out the dynamics. Step 1 is more straightforward in the adiabatic approximation, but carrying out dynamics in the adiabatic approximation involves vector couplings that are singular on high-dimensional, non-symmetry- determined seams and adiabatic surfaces with cuspidal ridges on those same seams. Therefore it is much more convenient to use a diabatic representation for dynamics. We have shown that the coherent switches with decay of mixing semiclassical trajectory method [1] is equally accurate in adiabatic and diabatic representations, and so we are pursuing methods for the convenient determination of diabatic states. We have previously developed the fourfold way for direct diabatization [2], and our group demonstrated it for applications to LiH, LiF, HBr, LiBr+, O3, Li + FH, H2 + H2, HNCO, NH3, CH2ClBr, BrCH2C(O)Cl, and CH3C(O)O-+ GCH2CH2G. Recently we showed how fourfold-way diabatization can be carried out at the multi-configuration quasidegenerate perturbation level (abbreviated MC-QDPT and comparable to multi-state CASPT2) with complete-active space self-consistent-field (CASSCF) diabatic molecular orbitals [3], and this method has now been incorporated in the HONDOPLUS and GAMESS electronic structure packages. We are now applying this scheme to obtain global potential energy surfaces and couplings for mode-specific photodissociation of phenol and for OH* + H2 -> OH + H2 and H2O + H. Recent progress will be presented. 1

[1] A. W. Jasper, S. Nangia, C. Zhu, and D. G. Truhlar, Acc. Chem. Res. 39, 101 (2006) [2] H. Nakamura and D. G. Truhlar, J. Chem. Phys., 115, 10353 (2001). [3] K. R. Yang, X. Xu, D. G. Truhlar, Chem. Phys. Lett., 573, 84 (2013)

O10 Probing Chemical Dynamics with Negative Ions

Daniel M. Neumark

Department of Chemistry University of California Berkeley, CA 94720

Negative ion photodetachment has been shown to be a versatile probe of transient species, including clusters, radicals, and transition states. This talk will present two types of photodetachment experiments that exemplify this capability. First, high resolution photoelectron spectroscopy experiments carried out using slow electron velocity map imaging (SEVI) of cryogenically-cooled anions will be discussed. Specific targets include metal oxide clusters, radicals of polycyclic aromatic hydrocarbons, and transition states of the F + H2 and F + CH4 reactions. Secondly, results on time-resolved radiation chemistry will be presented in which the dynamics of electron attachment to DNA bases are probed with femtosecond time resolution.

O11 Radical and Diradical Reactive Intermediates via Anion Photoelectron Imaging

Andrei Sanov

Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, U.S.A.

Anion photoelectron imaging is a powerful experimental technique to study the electronic structure of reactive intermediates, such as radicals and diradicals derived from closed-shell organic molecules. We will discuss recent results for several types of radicals, carbenes and other types of diradicals, derived from bond-breaking reactions in organic compounds. In particular, several C-H bond dissociation and ring-opening reactions will be discussed. Substitution effects on the thermodynamic stability of the radicals and the electronic state ordering in carbenes are examined through anion photoelectron spectra and photoelectron angular distributions. Reactive intermediates resulting from ring-opening reactions of hetero­ cyclic compounds, such as oxazole, exhibit particularly rich spectral features and electronic- structural properties. The assignment of the observed photodetachment bands to the low-lying electronic states of the resulting neutral intermediates is made possible by a combination of photoelectron spectra, angular distributions, and ab initio modeling. The photoelectron angular distributions in the photodetachment from hybrid spx orbitals, which are ubiquitous in chemistry, are interpreted using an approximate formalism developed specifically for such mixed-character states. These distributions provide insight into the degree of hybridization and aromaticity of the compounds studied.

O12 Ultraviolet photodissociation dynamics of the cyclohexyl radical

Michael Lucas, Yanlin Liu, and Jingsong Zhang

Department of Chemistry University of California at Riverside Riverside, CA 92521

The ultraviolet (UV) photodissociation dynamics of the cyclohexyl (c-C6 H11) radical was studied for the first time using the high-n Rydberg atom time-of-flight (HRTOF) technique. The cyclohexyl radical was produced by the 193 nm photodissociation of chlorocyclohexane and bromocyclohexane and was examined in the photolysis region of 232-262 nm. The H-atom photofragment yield (PFY) spectrum contains a broad peak centering around 250 nm, in good agreement with the UV absorption spectra of cyclohexyl. The translational energy distributions of the H-atom loss product channel, P(ET)’s, show a large translational energy release peaking at ~ 45 kcal/mol. The fraction of average translational energy in the total excess energy, f), is in the range of 0.45-0.57 from 232-262 nm. The H-atom product angular distribution is anisotropic with a positive f parameter in the range of 0.3-1, indicating a dissociation time scale faster than one rotation period of the radical. The translational energy release and anisotropy of the H-atom loss product channel are significantly larger than those expected for a statistical unimolecular dissociation of a hot radical, thus showing a non-statistical dissociation mechanism of this large radical. The dissociation mechanism is consistent with direct dissociation on a repulsive excited state surface or on the repulsive part of the ground state surface to produce cyclohexene + H, possibly mediated by conical intersection.

O13 Studies of Neutral Reaction Dynamics using Dissociative Photodetachment: HCO2 and F + H2O ^ HF + OH Robert E. Continetti

Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, 92093 CA, USA

Dissociative photodetachment (DPD) of anions has proven to be a valuable tool for the preparation of transient neutrals with known internal energies at critical regions on the potential energy surfaces governing neutral chemical reactions. We have made use of photoelectron- photofragment coincidence (PPC) spectroscopy to study the dissociation dynamics of these energy-selected species. These experiments are performed on a fast ion beam spectrometer, now equipped with a cryogenically cooled electrostatic ion beam trap to store the anions during the experiment.1 We have carried out studies of the spectroscopy and tunneling dynamics of the HOCO radical,12 and have now extended these studies to the formyloxyl radical HCO2 and the F + H2O ^ HF + OH reaction using the F (H2O) precursor anion. The studies of HCO2 were carried out near-threshold at a photon energy of 4.27 eV, where photodetachment of HCO2 accesses the three lowest-lying electronic states (2B2, 2A1, and 2A2) of the radical. The photoelectron spectrum is dominated by OCO bending excitation in the three states and structure in the PPC spectrum reveals that predissociation of HCO2 leads to a distribution of CO2 bending excited states that vary as a function of intermediate electronic state. These results can be directly compared to quantum dynamics calculations as a new probe of the potential energy surface that governs predissociation of HCO2 ^ H + CO2. The exothermic four-atom reaction F + H2O ^ HF + OH is an emerging benchmark in reaction dynamics. Crossed beam studies have revealed rich reaction dynamics including highly inverted vibrational distributions and non-adiabatic effects.3 Full six-dimensional treatments of the potential energy surface for this system remain theoretically challenging, but have recently become possible.4 We have made PPC measurements on the F (H2O) precursor anion at 4.8 eV and have observed DPD to both the higher lying F + H2O + e reactants and the lower energy HF + OH + e products, as well as photodetachment to the van der Waals well in the exit channel. Although the configuration of the nascent FH2O is more “reactant-like”, HF + OH products dominate, with a vibrational inversion in HF while the OH products are predominantly without vibrational excitation. The prospects for comparing these results to theory as well as studying the influence of vibrational excitation will be discussed. This work was funded by the United States Department of Energy, under grant number DE-FG03-98ER14879.

1 C.J. Johnson, B.B. Shen, B.L.J. Poad and R.E. Continetti, Rev. Sci. Instrum. 82, 105105 (2011). 2. C.J. Johnson, M.E. Harding, B.L.J. Poad, J.F. Stanton and R.E. Continetti, J. Am. Chem. Soc. 133, 19606-19609 (2011); C.J. Johnson, B.L.J. Poad, B.B. Shen and R.E. Continetti, J. Chem. Phys. 134, 171106 (2011). 3. A. M. Zolot, D. J. Nesbitt, J. Chem. Phys. 129, 184305 (2008) 4. J. Li, R. Dawes, H. Guo, J. Chem. Phys. 137, 094304 (2012)

O14 Quantum reaction dynamics studies of astrophysical interest below 100 K

Pascal Honvault

Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB UMR 6303 CNRS/universite de Bourgogne) 9 av. Alain Savary, BP 47870, 21078 DIJONcedex, France ; UFR Sciences et Techniques, Universite de Franche-Comte, Besangon, France

We are interested in the reactive collisions of astrophysical interest between open- shell atoms (C,N,O) and the hydroxyl radical OH. The ortho-para conversion of H2 through the H+ + H2(v=0,j) H+ + H2(v=0,j') reaction has also been studied, as well as the isotopic variant reaction D+ + H2 HD + H+. Opacity functions, product state-resolved integral cross-sections, differential cross sections, state-specific and thermal rate constants have been obtained by means of a time independent quantum mechanical (TIQM) approach [1] combined with high accuracy ab initio potential energy surfaces. The TIQM results are compared with experimental results (as available) and also with those obtained using a time dependent wave packet approach, the quasi-classical trajectory method and statistical methods [2-4].

[1] P. Honvault, J.-M. Launay, Theory of Chemical Reaction Dynamics; Lagana, A.;Lendvay, G., Ed.; Kluwer Dordrecht, The Netherlands, 2004, pp 187. [2] M. Jorfi, P. Honvault, J. Phys. Chem. A 113, 2316 (2009); J. Daranlot, M. Jorfi, C. Xie, A. Bergeat, M. Costes, P. Caubet, D. Xie, H. Guo, P. Honvault, K.M. Hickson, Science 334, 1538 (2011). [3] P. Honvault, M. Jorfi, T. Gonzalez-Lezana, A. Faure, L. Pagani, Phys. Rev. Lett. 107, 023201 (2011); Phys. Rev. Lett. 108, 109903 (2012). [4] P. Honvault, Y. Scribano, J. Phys. Chem. A, in press (2013).

O15 Controlling Collisions using Stark-decelerated molecular beams

Sebastiaan Y. T. van de Meerakker

Radboud University Nijmegen, Institute for Molecules and Materials, the Netherlands

Over the last years methods have been developed to get improved control over molecules in a molecular beam [1,2]. With the Stark decelerator, a part of a molecular beam can be selected to produce bunches of molecules with a computer-controlled velocity and with longitudinal temperatures as low as a few mK. The molecular packets that emerge from the decelerator have small spatial and angular spreads, and have almost perfect quantum state purity.

These tamed molecular beams are ideally suited for molecular scattering experiments, and allow for precise state-to-state scattering experiments as a function of the collision energy. I will report on low-energy scattering of OH with rare gas atoms, revealing the quantum threshold behavior of state-to-state inelastic cross sections [3,4]. Recently, we have exploited the state purity of Stark decelerated beams to study inelastic scattering between two state-selected molecules, using the two open shell radicals OH + NO as a model system [5]. Finally, I will present our first results on the combination of Stark deceleration and velocity map imaging. The narrow velocity spread of Stark-decelerated beams results in scattering images with an unprecedented sharpness and angular resolution. This has facilitated the observation of diffraction oscillations in the state- to-state differential cross sections for NO + Ar.

1. S.Y.T. van de Meerakker, H.L. Bethlem, and G. Meijer, Nature Physics 4, 595 (2008). 2. S.Y.T. van de Meerakker, H.L. Bethlem, N. Vanhaecke, and G. Meijer, Chemical Reviews 112, 4828 (2012). 3. J.J. Gilijamse, S. Hoekstra, S.Y.T. van de Meerakker, G.C. Groenenboom, and G. Meijer Science 313, 1617 (2006). 4. L. Scharfenberg, J. Klos, P.J. Dagdigian, M.H. Alexander, G. Meijer, and S.Y.T. van de Meerakker Phys. Chem. Chem. Phys. 12, 10660 (2010). 5. M. Kirste, X. Wang, H.C. Schewe, G. Meijer, K. Liu, A. van der Avoird, L.M.C. Janssen, K.B. Gubbels, G.C. Groenenboom, and S.Y.T. van de Meerakker Science 338, 1060 (2012).

O16 Travelling-Wave Deceleration of Buffer-Gas Beams of CH

Maya Fabrikant (JILA) Noah Fitch (JILA) Nicholas Farrow (JILA) Tian Li (University of Nevada, Reno) Jonathan Weinstein (University of Nevada, Reno) Heather Lewandowski (JILA)

Buffer-gas beams are a promising method for the production of bright sources of cold molecules. We have created ground state CH radicals in a buffer-gas cell to produce a cold molecular beam of 1011 mol./pulse. However, slowing and trapping molecules created in these sources presents challenges because of large pulse lengths and velocity spreads compared to more familiar supersonic beams. Traveling-wave decelerators are uniquely suited to meet these challenges because of their ability to confine molecules in three dimensions during deceleration and their versatility afforded by analog control of the electrodes. We present a protocol for Stark deceleration of beams with a large velocity spread for use with a travelling-wave decelerator. Our method involves confining molecules transversely with a hexapole for an optimized distance before deceleration, which precisely rotates the phase-space distribution of the molecules so that the portion of the packet that enters the decelerator always matches the phase-space acceptance. We demonstrate with simulations that using this method, we can effectively decelerate a significant portion of the molecules in many successive wells that may then be combined and trapped.

O17 Ultracold hydrogen atoms: a versatile coolant for producing microkelvin molecules

Jeremy M. Hutson and Maykel Leonardo Gonzalez-Martinez

Joint Quantum Centre Durham/Newcastle, Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, United Kingdom

e-mail: [email protected]

There are several experimental methods that are capable of producing samples of molecules such as ND3, OH and NH at temperatures of 10 to 100 mK in electrostatic or magnetic traps. These include helium buffer-gas cooling and molecular beam deceleration. However, there is so far no way to transfer these cold molecules to the ultracold regime below 1 mK. Ultracold molecules would offer a wide range of opportunities for quantum simulation, quantum information processing, and the development of a controlled molecular assembly in which chemical transformations are carried out coherently on an entire sample of molecules. Sympathetic cooling, in which cold species are cooled further by thermal contact with ultracold atoms, usually alkali metals, has been used successfully for atoms and molecular ions but has not yet been achieved for neutral molecules. The difficulty is that molecules are usually trapped in states that are not the lowest in the field used to trap the molecules, and can undergo inelastic (deexcitation) collisions that release kinetic energy and eject both collision partners from the trap. We have explored sympathetic cooling theoretically in many different systems, in order to find collision partners that do not have this problem. We have found that, in general, light collision partners are favourable for sympathetic cooling because inelastic collisions are suppressed by centrifugal barriers at low fields and low collision energies. However, even atoms such as Li [1] and Mg [2] are predicted to succeed only at temperatures below about 10 mK, which is on the edge of what is experimentally achievable. In an exciting development, we have recently discovered that ultracold hydrogen atoms, which can be produced at very high densities at temperatures down to 50 pK, have very favourable properties for sympathetic cooling. The potential energy surfaces for (spin-polarised) interactions of H with NH and OH are quite weakly anisotropic and the centrifugal barriers are very high. We predict that sympathetic cooling with ultracold H atoms can succeed from starting temperatures as high as 1 K, which are much easier to achieve. 1

[1] A. O. G. Wallis, E. J. J. Longdon, P. S. Zuchowski and J. M. Hutson, Eur. Phys. J. D, 2011, 65, 151. [2] A. O. G. Wallis and J. M. Hutson, Phys. Rev. Lett., 2009, 103, 183201.

O18 Probing Gas-Liquid and Gas-SAM Interfaces with Quantum State Resolved Collision Dynamics

Andrew W. Gisler, Rob Roscioli, Amelia Zutz, and David J. Nesbitt, * * JILA, National Institute of Standards and Technology, and University of Colorado, Boulder, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA

Skimmed molecular beams, supersonic cooling, low vapor pressure liquids under single collision conditions and quantum state-resolved detection of the scattered species provide a unique suite of tools for experimental and theoretical study of collision dynamics at the gas-liquid and gas- condensed phase interface. This talk will address recent progress in our group in the following areas. 1) High resolution IR laser absorption studies of molecular scattering from “salty” hydrogen bonded liquids, which provide novel evidence for the presence of excess negative ion density at the gas-liquid interface. 2) Quantum state-to-state resolved scattering of supersonically cooled HCl from self assembled monolayers on Au(111)/mica, utilizing REMPI and velocity map imaging to probe correlations between rotational and translational excitation in the collision event. The role of strong interaction between first principles theory and experiment will be emphasized.

O19 Dynamics of Methane Dissociation on Ni and Pt Surfaces

Bret Jackson

Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA

The rate-limiting step in the steam reforming of methane is the dissociative chemisorption of methane on a Ni catalyst. DFT-based electronic structure methods are used to map out reaction pathways for this process on several Ni and Pt surfaces, and a full­ dimensional fully quantum reaction path model is used to compute state-resolved dissociative sticking probabilities. This model is based on an expansion in the adiabatic vibrational states of the methane molecule, and a sudden approximation is used to incorporate the effects of lattice motion. The barriers to reaction vary with lattice motion for all surfaces, leading to a strong increase in reactivity with temperature. Comparisons are made with recent experiments on Ni(100), Ni(111), Pt(111) and Pt(110)-(1x2). Our model successfully explains the magnitude of the reactivity, its variation with energy and temperature, and the observed increase in reactivity with vibrational excitation of the methane1,2.

1. B. Jackson and S. Nave, J. Chem. Phys. 135, 114701 (2011).

2. B. Jackson and S. Nave, J. Chem. Phys. 138, 174705 (2013).

O20 Charge transfer reactions induce Born-Oppenheimer breakdown in surface chemistry: Applications of double resonance spectroscopy in molecule-surface scattering

Alec M. Wodtke

Georg-August University of Gottingen and the Max Planck Institute for Biophysical Chemistry, Gottingen, Germany

Atomic and molecular interactions constitute a many-body quantum problem governed fundamentally only by the Coulomb forces between many electrons and nuclei. While simple to state, computers are simply not fast enough to solve this problem by brute force, except for the simplest examples. Combining the Born-Oppenheimer Approximation (BOA) with Density Functional Theory (DFT), however, allows theoretical simulations of extraordinarily complex chemical systems including molecular interactions at solid metal surfaces, the physical basis of surface chemistry. This lecture describes experiments demonstrating the limits of the BOA/DFT approximation as it relates to molecules interacting with solid metal surfaces. One of the most powerful experimental tools at our disposal is a form of double resonance spectroscopy, which allows us to define the quantum state of the molecule both before and after the collision with the surface, providing a complete picture of the resulting energy conversion processes. With such data, we are able to emphasize quantitative measurements that can be directly compared to first principles theories that go beyond the Born-Oppenheimer approximation. One important outcome of this work is the realization that Born-Oppenheimer breakdown can be induced by simple charge transfer reactions that are common in surface chemistry.

Related References [1] White, J.D., J. Chen, D. Matsiev, D.J. Auerbach, and A.M. Wodtke, Nature, 2005. 433(7025): 503-505. [2] Huang, Y.H., C.T. Rettner, D.J. Auerbach, and A.M. Wodtke, Science, 2000. 290(5489): 111-114. [3] Cooper, R., I. Rahinov, Z.S. Li, D. Matsiev, D.J. Auerbach, and A.M. Wodtke, Chemical Science, 2010. 1(1): 55-61. [4] Shenvi, N., S. Roy, and J.C. Tully, Science, 2009. 326 (5954): 829-832. [5] Larue, J., T. Schafer, D. Matsiev, L. Velarde, N.H. Nahler, D.J. Auerbach, and A.M. Wodtke, Physical Chemistry Chemical Physics, 2011. 13(1): 97-99.

O21 Mode/Bond Selectivity in Methane Dissociative Chemisorption on Ni(111)

Bin Jiang, 1 Rui Liu,*2 Jun1 Li,1 Daiqian Xie,3 Minghui Yang, 2 and HuaGuo 1

department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico, 87131, USA 2Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Centre for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China 3 Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China

Dissociative chemisorption of CH4 on Ni(111) is not only of industrial importance as the rate-limiting step in methane steam reforming, but also a prototype for understanding heterogeneous catalysis on transition-metal surfaces. The mode and bond selectivities have been experimentally observed in this reaction, which have recently attracted many theoretical activities, although a deep understanding is still lacking. 1 Towards this goal, a twelve­ dimensional global potential energy surface has been developed for CH4 interacting with a rigid Ni(111) surface, based on a large number of density functional theory points, using a permutationally invariant polynomial fitting approach, which preserves the permutation symmetry in methane.2 The mode-selectivity has been investigated quantum mechanically (QM) using an eight-dimensional model, which includes representatives of all four vibrational modes of methane. After correcting for surface effects, key experimental observations, including the mode selectivity, are well reproduced. 2 The bond and mode-selectivities of the deuterated methanes have been studied using quasi-classical trajectory (QCT) calculations. The calculated reaction probabilities near and above the reaction barrier reproduced the general trends observed in experimental investigations of various vibrationally excited CH4, CH3D, and CH2D2 species on nickel 3 surfaces. All theoretical results can be explained using the recently proposed Sudden Vector Projection (SVP) model.4

References: 1 L. B. F. Juurlink, D. R. Killelea and A. L. Utz, Prog. Surf. Sci. 84, 69 (2009). 2 B. Jiang, R. Liu, J. Li, D. Xie, M.-H. Yang and H. Guo, Chem Sci, in press (2013). 3 B. Jiang and H. Guo, J. Phys. Chem. C submitted (2013). 4 B. Jiang and H. Guo, J. Chem. Phys. 138, 234104 (2013).

O22 Towards a chemically accurate description of reactive molecule-surface scattering.

Geert-Jan Kroes,

Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands

Achieving chemical accuracy in the theoretical description of reactive scattering at metal surfaces requires a chemically accurate description of the molecule-metal surface interaction and the dynamics of the involved molecule(s), and may additionally require an accurate description of surface phonons and electron-hole pair excitation. We have recently shown that a chemically accurate description of the molecule-surface interaction is possible with a novel implementation of specific reaction parameter density functional theory (SRP-DFT) for the H2 + Cu(111) system. The SRP density functional derived for H2 + Cu(111) is transferable to H2 interacting with another low index face of copper, i.e., the (100) face. An improved description of reactive scattering in the early barrier system H2 + Ru(0001) can be obtained with SRP density functionals incorporating a description of the van der Waals interaction. Attempts to derive SRP density functionals describing the dissociative chemisorption of methane on Pt(111) are in progress. Progress with research on the effect of surface temperature on metal-surface reactions will also be reported. Recent Ab Initio Molecular Dynamics (AIMD) calculations on D2 + Cu(111) have shown that incorporating the effect of surface temperature leads to a significally improved agreement with experiment for the dependence of the dissociative chemisorption probability on molecular orientation. Not only the instantaneous displacement of the surface atoms and dynamical recoil, but also surface thermal expansion may affect the reactivity. The latter effect is especially important for open surfaces like the Cu(100) face. Reproducing reaction probabilities and their surface temperature dependence challenges the existing density functionals, which not only are poor at predicting reaction barrier heights, but also do not yet yield a simultaneously accurate description of reaction barrier heights and crystal lattice constants.

O23 Simulations of X- + CH3Y Ion-Molecule Reactions. Roles of Non-Statistical Dynamics, Multiple Reaction Pathways, and Microsolvation

William L. Hase

Department of Chemistry and Biochemistry Texas Tech University Lubbock, TX 79409

In recent research molecular beam, ion-imaging experiments and direct dynamics simulations have been combined to attain an understanding of the atomic-level mechanisms of X- + CH3Y ion-molecule reactions.1-6 This work has confirmed previous studies of these reactions, indicating the importance of non-statistical reaction dynamics. Both SN2 nucleophilic substitution and proton transfer are important reaction pathways. The simulations reveal that the reactions occur by a number of different direct and indirect reaction mechanisms, including direct rebound and stripping, and indirect hydrogen-bonding, ion-dipole complex, and roundabout. Microsolvation has important effects on the reaction dynamics. The experiments and simulations are in very good agreement.

1. J. Mikosch, S. Trippel, C. Eishhorn, R. Otto, U. Lourderaj, J. X. Zhang, W. L. Hase, M. Weidemuller, and R. Wester, “Imaging Nucleophilic Substitution”, Science 319, 183 (2008). 2. J. Zhang, J. Mikosch, S. Trippel, R. Otto, M. Weidemuller, R. Wester, and W. L. Hase, “F- + CH3I Reaction Dynamics. Non-Traditional Atomistic Mechanisms and Formation of a Hydrogen-Bonded Complex”, J. Phys. Chem. Lett. 1, 2747 (2010). 3. R. Otto, J. Xie, J. Brox, S. Trippel, M. Stei, T. Best, M. R. Siebert, W. L. Hase, and R. Wester, “Reaction Dynamics of Temperature-Variable Anion Water Clusters Studied with Crossed Beams and by Direct Dynamics”, Faraday Discuss. Chem. Soc. 157 , 41 (2012). 4. J. Mikosch, J. Zhang, S. Trippel, C. Eichhorn, R. Otto, R. Sun, W. A. de Jong, M. Weidemuller, W. L. Hase, and R. Wester, “Indirect Dynamics in a Highly Exoergic Substitution Reaction”, J. Am. Chem. Soc. 135 , 4250 (2013). 5. J. Zhang, U. Lourderaj, R. Sun, J. Mikosch, R. Wester, and W. L. Hase, “Simulation Studies of the Cl- + CH3I Sn2 Nucleophilic Substitution Reaction: Comparison with Imaging Experiments”, J. Chem. Phys. 138, 114309 (2013). 6 . J. Xie, R. Sun, M. R. Siebert, R. Otto, R. Wester, and W. L. Hase, “Direct Dynamics Simulations of the Product Channels and Atomistic Mechanisms for the OH- + CH3I Reaction. Comparison with Experiment”, J. Phys. Chem. A 117, xxxx (2013).

O24 Rydberg Tagging of Spin-Polarized Hydrogen Atoms

Bernadette M. Broderick 1, Yumin Lee1, Michael B. Doyle 1,

Oleg S. Vasyutinskii2, and Arthur G. Suits1

department of Chemistry, Wayne State University, Detroit, MI 48202 2Ioffe Institute, Russian Academy of Sciences, St. Petersburg, 19401 Russia

We present an experimental technique allowing for direct measurement of the velocity dependence of the spin polarization of hydrogen atoms with high resolution and high sensitivity. The strategy (Fig. 1) is a simple adaptation of the H atom "Rydberg tagging" approach widely used in photodissociation and reactive scattering studies. The method is demonstrated with application to photodissociation of several systems. The results are in good agreement with theoretical predictions in the limited cases where they are available. The technique is suitable as a general probe of the velocity dependence of H atom spin polarization in photodissociation and reactive scattering. Strategies to adapt this approach to imaging measurements will be highlighted but have not yet been demonstrated.

(Unresolved Fine Structure) 366 nm

0.38 cm

121.6 nm

Figure 1. Excitation scheme for Rydberg tagging of spin-polarized H atoms.

O25 Dynamics of bimolecular polyatomic reactions on ab initio potential energy surfaces

Gabor Czako

Institute of Chemistry, Eotvos University, Budapest, Hungary

Recent experimental and theoretical studies on X + methane abstraction and X” + CH3Y substitution reactions extended and modified our fundamental knowledge on chemical reactivity. The two key steps of the dynamical simulations of these reactions are the computation of the potential energy surface (PES) and the solution of the nuclear motion problem on the PES. In the past few years we developed chemically accurate ab initio PESs for the X + CH4 (X = F, Cl, Br, O(3P)) [1-4] and F- + CH3Cl ^ Cl” + CH3F [5] reactions and investigated their dynamics using the quasiclassical trajectory (QCT) method, thereby supporting and explaining the experimental findings and sometimes inspiring new experiments. Here, we present our most recent results on the above reactions, such as (a) dynamics of the O(3P) + CH4, CD4, CHD3 abstraction reactions [4,6], showing the theory vs. experiment and QCT vs. quantum comparisons, (b) dynamics of the Cl + CH4 ^ H + CH3Cl substitution reaction focusing on the polyatomic product analysis [7], (c) PES and dynamics of the Br + CH4 reaction [3], (d) rotational effects on the reactivity of Cl + CHD3, and (e) PES and dynamics of the F- + CH3Cl ^ Cl- + CH3F Sn2 reaction [5].

[1] G. Czako, B. C. Shepler, B. J. Braams, and J. M. Bowman, J. Chem. Phys., 2009, 130, 084301. [2] G. Czako and J. M. Bowman, Science, 2011, 334, 343. [3] G. Czako, J. Chem. Phys., 2013, 138, 134301. [4] G. Czako and J. M. Bowman, Proc. Natl. Acad. Sci. U.S.A., 2012, 109, 7997. [5] I. Szabo, A. G. Csaszar, and G. Czako, 2013, in preparation. [6] G. Czako, R. Liu, M. Yang, J. M. Bowman, and H. Guo, J. Phys. Chem. A, 2013, submitted. [7] G. Czako, J. Phys. Chem. A, 2012, 116, 7467.

O26 Quantum Dynamics of Methane-Atom Reactions

Uwe Manthe

Theoretische Chemie, Fakultat fur Chemie, Universitat Bielefeld Universitatstr. 25, 33615 Bielefeld, Germany

Reactions of methane with atoms as H, Cl(2P), F(2P), or O(3P) are benchmark examples of polyatomic reactions. In this talk, accurate full-dimensional quantum dynamics calculations studying the H+CH4 and F(2P)+CH4 reactions will be presented. These calculations use the multi-configurational time-dependent Hartree (MCTDH) approach to efficiently and accurately propagate high-dimensional wave packets. For the H+CH4 -> H2+CH3 reaction, state-resolved reaction probabilities are obtained using a rigorous quantum transition state concept and an accurate potential energy surface.

To investigate the dynamics in entrance channel of the F(2P)+CH4 reaction, the photo­ ionization of the CH4F- anion is studied. Coupled diabatic potential energy surfaces describing the vibronic and spin-orbit coupling are developed and the resonance structures observed in the experimental photo-detachment spectra are addressed.

O27 Vibrationally Resolved Dynamics and Energy Flow for Reactions in Solution

A. J. Orr-Ewing,1 G.T. Dunning,1 F. Abou-Chahine,1 D.R. Glowacki,1 J.N. Harvey,1 S.J. Greaves, 2 G.M. Greetham,3 I.P. Clark, 3 and M. Towrie3

1 School of Chemistry, University of Bristol, Cantock ’s Close, Bristol BS8 ITS, UK 2 School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK 3 Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK

Under isolated collision conditions, exothermic reactions with transition states that lie early along the reaction coordinate favour vibrational excitation of the newly formed reaction products. Such behaviour has been confirmed for gas phase reactions in numerous experiments using techniques such as infra-red chemiluminescence, LIF, or velocity map imaging. Complementary study of these types of reaction in solution in liquids provides an opportunity to examine how the solvent modifies reactive potential energy surfaces and how the associated reaction dynamics change in a highly collisional environment. Time-resolved infra-red absorption spectroscopy enables us to search for evidence of product vibrational excitation, but requires picosecond time resolution to compete with relaxation of any such vibrationally excited products by loss of excess energy to the surrounding solvent bath.

We have previously reported observation of vibrationally excited HCN (and DCN) from the reactions of CN radicals with organic molecules such as cyclohexane (and d 12-cyclohexane) in various solvents [1-4]. The vibrational excitation is initially localized in the C-H stretch and bending excitations, and computational simulations not only reproduce the observed dynamics, but also provide important new insights concerning energy flow from the vibrationally hot reaction products [5]. These studies have since been extended to exothermic reactions of Cl and F atoms in various organic solvents [6,7], for which we are also able to quantify branching to vibrationally excited products and the timescales for relaxation by coupling to the solvent. The most recent results from our experimental and computational studies will be presented. 1 2 3 4 5 6 7

[1] S.J. Greaves, R.A. Rose, T.A.A. Oliver, D.R. Glowacki, M.N.R. Ashfold, J.N. Harvey, I.P. Clark, G.M. Greetham, A.W. Parker, M. Towrie and A.J. Orr-Ewing, Science, 331, 1423 (2011). [2] A.J. Orr-Ewing, D.R. Glowacki, S.J. Greaves and R.A. Rose, J. Phys. Chem. Lett. 2, 1139 (2011). [3] R.A. Rose, S.J. Greaves, T.A.A. Oliver, I.P. Clark, G.M. Greetham, A.W. Parker, M. Towrie, and A.J. Orr-Ewing, J. Chem. Phys. 134, 244503 (2011). [4] R.A. Rose, S.J. Greaves, F. Abou-Chahine, D.R. Glowacki, T.A.A. Oliver, M.N.R. Ashfold, I.P. Clark, G.M. Greetham, M. Towrie and A.J. Orr-Ewing, PCCP 14, 10424­ 10437 (2012). [5] D.R. Glowacki, R.A. Rose, S.J. Greaves, A.J. Orr-Ewing and J.N. Harvey, Nature Chem. 3, 850 (2011). [6] S.J. Greaves, G.T. Dunning, A.J. Orr-Ewing, G.M. Greetham, I.P. Clark, and M. Towrie, Chem. Sci. 4, 226-237 (2013). [7] G.T. Dunning, F. Abou-Chahine, D.R. Glowacki, J.N. Harvey, G.M. Greetham, I.P. Clark, M. Towrie and A.J. Orr-Ewing, in preparation (2013).

O28 Dynamics of quantum rotors in complex environments

Pierre-Nicholas Roy, Tao Zeng, and Gregoire Guillon

Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada

We will present approaches for the study molecular rotors embedded in superfluid environments. We will mostly focus on path integral simulation techniques and will consider both atomic and molecular bosons as the constituent of the superfluid. We will show that the superfluid response to the rotational dynamics of a molecule can be used to explain microwave and infrared spectroscopic experiments [1,2]. We will discuss the challenges associated with different types of rigid tops [3]. The question of angular momentum projection axis for the calculation of superfluid fraction will be addressed. Results will be presented for the case of asymmetric top molecules trapped in parahydrogen clusters and the idea of a genuine probe of superfluid response will be introduced. The molecular symmetry of the asymmetric top probes and implications regarding experimental measurements will be discussed.

References 1. H Li, R. J. Le Roy, P.-N. Roy, A.R.W. McKellar, Phys. Rev. Lett. 105, 133401 (2010). 2. P. L. Raston, W. Jager, H. Li, R. J. Le Roy, and P.-N. Roy Phys. Rev. Lett. 108, 253402 (2012). 3. T. Zeng, H. Li, and P.-N. Roy, , J. Phys. Chem. Lett. 4, 18 (2013).

O29 Dissociation and Isomerization in Clusters and Solution

Cornelia Heid, Amanda Case, T.J. Preston, and F. Fleming Crim

Department of Chemistry University of Wisconsin - Madison Madison, Wisconsin 53706

Isomerization occurs in vibrationally excited molecules, in either ground or excited electronic states, as they explore geometries in which bonds can reorganize. In excited states, these processes often involve conical intersections, and it is also possible for interactions with the surroundings to turn a simple dissociation into an isomerization. One of first steps toward studying the influence of the surroundings is to examine the dynamics of small clusters. We have studied the dissociation of ammonia dimers and trimers to determine the strength of their bonds and to discover the pathways energy disposal. A similar study of the mixed complex of ammonia with aminophenol reveals more complicated behavior in which the added vibrational energy induces an isomerization of the aminophenol molecule, apparently moderated by the presence of the ammonia partner. It is possible to extend these types of studies into liquids using the high temporal resolution of ultrafast lasers. We have observed that the simple gas-phase dissociation of a halomethane becomes an isomerization that forms less-stable species in the presence of surrounding molecules.

O30 Inert Gas Scattering from Liquid Hydrocarbon Microjets

Diane K. Lancaster, Alexis M. Johnson, Justin M. Wiens, GilbertM, Nathanson

University of Wisconsin, Madison

Collisions between gases and liquids control energy and mass transfer in many processes, including the heating and evaporation of hydrocarbon fuels in jet engines. The dynamics of these collisions can be investigated by scattering experiments utilizing molecular beams and continuously renewed liquid surfaces in vacuum. Earlier scattering experiments relying on a liquid-coated wheel were limited to vapor pressures of less than 0.005 Torr, excluding liquids such as jet fuel and water. Narrow diameter liquid jets circumvent this limitation because they generate a thin vapor blanket that can be penetrated by gas molecules without undergoing gas- vapor collisions. The use of ~10 micron radius microjets potentially expands the vapor pressure range to several Torr for water, though smaller vapor pressures are required for larger molecules. Our first experiments focus on collisions of inert gases with liquid dodecane (0.1 Torr vapor pressure), the dominant component of a common jet fuel surrogate. We have explored collisions of oxygen (Einc = 30 kJ/mol, 9 kJ/mol) and neon (Einc = 50 kJ/mol, 6 kJ/mol) with dodecane and compared them to collisions with a low vapor pressure liquid, squalane (10-8 Torr). The extent of energy transfer and thermalization are remarkably high and similar for the two hydrocarbon liquids. These studies suggest that ambient gas molecules readily transfer energy and heat fuel droplets during the combustion process.

O31 Multiple Resonance Methods for Conformation-Specific Spectroscopy and Dynamics

Timothy S. Zwier

Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084 U.S.A.

This talk will describe UV-UV and IR-UV double resonance methods for recording single­ conformation spectra and probing the dynamics of large, flexible neutral molecules, ions, radicals, and molecular clusters. Several recent studies from our group will illustrate the types of information to be gleaned from such studies. First, the effects of individual solvent molecules on interchromophore coupling will be described in water-containing 1,2- diphenoxyethane clusters, DPOE-(H2O)n, n=1-4.5 Population transfer methods are used to study conformational isomerization in the DPOE monomer and the conformational product distribution formed by IR photofragmentation of the DPOE-H2O complex. Second, single­ conformation IR spectra of model synthetic foldamers along a series of constrained y-, a/y-, and p/y-peptides will be used to study the way in which constraints serve to direct the folding of these synthetic peptidomimetics. Finally, first results from a new cryo-cooled ion trap instrument will also be described, focusing on the IR and UV spectroscopy of singly- charged Leu-enkephalin in protonated, sodiated, and methoxy-capped forms. We will connect our results with past CID studies of protonated peptides that are typically interpreted in terms of “mobile proton” theory. 1

1 L. B. F. Juurlink, D. R. Killelea and A. L. Utz, Prog. Surf. Sci. 84, 69 (2009). 2 B. Jiang, R. Liu, J. Li, D. Xie, M.-H. Yang and H. Guo, Chem Sci, in press (2013). 3 B. Jiang and H. Guo, J. Phys. Chem. C submitted (2013). 4 B. Jiang and H. Guo, J. Chem. Phys. 138, 234104 (2013). 5 E. G. Buchanan, J. R. Gord and T. S. Zwier, Journal of Physical Chemistry Letters 4, 1644 (2013). 6 J. M. Beames, F. Liu, L. Lu and M. I. Lester, J. Am. Chem. Soc. 134, 20045 (2012). 7 O. Welz, J. D. Savee, D. L. Osborn, S. S. Vasu, C. J. Percival, D. E. Shallcross and C. A. Taatjes, Science 335, 204 (2012).

O32 Chemical Dynamics of Complex Reactions with Bio-molecules: the Case of Restriction Enzymes in Highly Packed DNA Brushes (*)

G. Scoles, FRS

Universita’ di Udine, Azienda Ospedaliero Universitaria S. Maria della Misericordia, Pad # 13 Anatomia Patologica, Udine, UD 33100, Italy

It is typical of large bio-molecules to reactwith each other after mutual recognition at the reactive site. In the case of restriction enzymes i.e. enzymes that cut DNA molecules, the recognition happens at a restriction site consisting of four pre-specified base pairs. It is reasonably well known that before the cutting reaction can proceed the presence is required of relatively large proteins and particularbuffer conditions. There exists however a class of enzymes that at the cost of having two extrabase pairs for recognition dispose of the other requirements. All of the above refers to reaction in solution but clearly also when the DNA is bound to a surface, forming a brush-like system, similar rules also apply. We have studied the restriction reaction of DPNII with ds-DNA oligomers (44 base pairs with a restriction site at half height) linked to a flat gold surface by Nanografting (Ref.1) by means of a C6 thiol group, at variable packing densities. A successful restriction reactions leads to a 50% decrease of the brush height with respect to the surrounding surface, that we measure by AFM. We have found that if the DNA coverage is low, the enzyme behaves naturally as in solution, but if the DNA density is above a certain critical point, the restriction reaction cannot proceed. We will also report the action of BAMH-1 (an enzyme that requires two extra GC pairs for high fidelity recognition) on the cutting of another ds-DNA brush polymer of 44 bases where we found the rather unremarkable result of normal behavior as in the case of DPNII. Very surprisingly, when we verifiedthat a DNA oligomer containing only the 4 base pairs restriction site that is not cut in solution, we found that beyond the normal not cutting at low coverage and not cutting at high coverage there was a small region of densities (just before the enzymes stops diffusing into the DNA brush) where the BMH-1 did clearly cut the DNA oligomer at its restriction site. More work will be necessary before we can demonstrate that what is clearly suggested by this measurements is correct: i.e. that it is the time the two molecules spend “together” more than the contact at recognition sites that primarily determines the outcome of the reaction. We found the above conclusion very interesting and we plan to investigate it further with the help of molecular simulations (*) This work was conducted with the collaboration of M. Castronovo, D. Choi, V. Inverso, S.K Redhu, and A.W. Nicholson mostly but not exclusively in the lab of M.C. at Temple Uniersity in Philadelphia.

References: [1] Liu, M.; Amro, N. A.; Liu, G. Nanografting for Surface Physical Chemistry. Annual Review of Physical Chemistry 2008, 59, 367-386. [2] Castronovo, M.; Lucesoli, A.; Parisse, P. et al. and Scoles, G. Two-dimensional Enzyme Diffusion in Laterally Confined DNA Monolayers. Nature Comm. 2011, 1-10. Addendum: Our findings demonstrate that, in crowded systems, enzyme may work very differently than in solutions. In general our findings are opening the door to novel applications of DNA nano-assemblies in both the fields of bio­ sensing and fundamental biophysics via the control of diffusion of enzymes on surfaces

O33 Potential Energy Surfaces

Joel M. Bowman

Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322

The potential energy surface (PES) is central to the theoretical description of the dynamics of molecular collisions and molecular vibrations. My talk will begin with a brief historical review of the development of the PES, with a focus on reactive systems, which present the biggest challenge to theory. The recent progress in representing a data set of ab initio electronic energies by a PES will be reviewed with a focus on our work, which explicitly incorporates the invariance of the PES with respect to all permutations of like atoms. Examples, including dynamics, will be given. These will range from the reactions of X +CH4, (X = H, F, Cl and O), the reactive electronic quenching of OH* by H2, “roaming” in CH3NO2 dissociation, and photodissociation of NO3 and also the bimolecular reaction O(3P)+NO2, to the IR spectra and dynamics of water clusters and ice, the complexes F-(H2O)2, HCl-OH, and the fluxional cations H5 + and H7+. All of these systems have been studies experimentally recently and comparisons with them will be also be presented.

Acknowledgements: Great thanks to Bastiaan Braams, Stuart Carter, Yimin Wang, John Mancini, Chen Qu, Zahra Homayoon, Xiaohong Wang, Hank Liu, Riccardo Conte, Gabor Czako, Eugene Kamarchik, Bina Fu and also to the Army Research Office, Department of Energy, National Science Foundation, and National Aeronautics and Space Administration for financial support.

O34 On the Formation of Interstellar Organo Silicon Molecules

Ralf I. Kaiser,1 Dorian Parker,1 Alexander Mebel,2 MusahidAhmed, 3 Martin Head-Gordon 4

University of Hawaii at Manoa 2 Florida International University 3 Lawrence Berkeley National

Laboratory 4 University of California at Berkeley

During the last decade, the molecular processes involved in the formation of organosilicon molecules have received considerable attention from the astrochemistry community. This is due to the key role of silicon-bearing molecules in the formation of silicon carbide dust grains in the outflow of circumstellar envelopes of carbon rich Asymptotic Giant Branch (AGB) stars like IRC+10216, where temperatures can rise up to a few 1,000 K close to the photosphere of the central star. IRC+10216 acts as a natural laboratory to understand the synthesis of organosilicon molecules and their connection to dust formation. However, the basic molecular processes, which link the circumstellar silicon and carbon chemistries, are far from being understood. Here, we present data on the chemical dynamics of reactions of silicon-bearing diatomic radicals exploiting supersonic beams of silicon nitride (SiN(X2Z+)) and of D1-silylidyne (SiD(X2n)) radicals - species which are isoelectronic to the cyano (CN(X2Z+)) and methylidyne (CH(X2n)) radicals. With respect to silicon nitride (SiN(X2Z+)), we explored the reaction dynamics with acetylene (C2H2(X1Eg+)) and with ethylene (C2H4(X1Ag)) and compared the reaction mechanisms with those of isoelectronic cyano radicals (CN(X2Z+)). The detection of silaisocyanoacetylene (HCCNSi) and silaisocyanoethylene (C2H3NSi) under single collision conditions manifested the formation of two representatives of a hitherto elusive class of molecules: silaisocyanides (Figure 1). We also probed the reaction dynamics of the deuterated counterpart of the simplest silicon­ bearing diatomic radical, D1-silylidyne (SiD(X2n)), with acetylene (C2H2(X1Eg+)). Pooled toge­ ther with ab initio calculations, we demonstrate that the silacyclopropenylidene molecule (c- SiC2H2) can be synthesized in the gas phase under single collision conditions via the barrier-less and slightly exoergic reaction (Figure. 2). This system denotes the simplest representative of a previously overlooked reaction class, in which the formation of an organosilicon molecule can be initiated via barrier-less reactions of silylidyne radicals with hydrocarbons. To further characteri­ ze the SiC2Hx (x =0,1,2) system, we conducted experiments at the Advanced Light Source. Four hydrogen-deficient organosilicon molecules were generated in situ via laser ablation of silicon and seeding the ablated species in acetylene gas, which acts simultaneously as a carrier and a re­ actant. By recording photoionization efficiency curves (PIE) and simulating the experimental spectrum with computed Franck Condon factors, we reproduced the general pattern of the PIE curves of m/z = 54 (SiC2H2+), 53 (SiC2H+), and 52 (SiC2+) identifying four (hydrogenated) sili­ con-carbon clusters and determining their ionization energies: c-SiC2 [9.75±0.10 eV], l-HCCSi [7.00±0.05 eV], c-SiC2H [7.27±0.05 eV], and c-SiC2H [9.05±0.05 eV]. These data will guide prospective astronomical identifications of these important organo silicon molecules utilizing the recently commissioned ALMA (Atacama Large Millimeter/sub-millimeter Array)

O35 Imaging bond breaking in hydrogen-bonded dimers and trimers

A.K. Samanta, L.C. Ch’ng, andH. Reisler

Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482

This talk will describe recent studies of state-to-state vibrational predissociation (VP) dynamics of small hydrogen bonded clusters following vibrational excitation. Velocity map imaging and REMPI are used to determine accurate bond dissociation energies (D0) of (H2O)2, (H2O)3, and other small dimers and trimers. Measured product energy distributions from the VP of these complexes are compared to theoretical models and insights into mechanisms are obtained from the quasi-classical trajectory (QCT) calculations of Czako, Wang, and Bowman. The prototype for pairwise interactions is the water dimer, while non-pairwise (cooperative) interactions are important for the smallest network - the water trimer. The imaging methodology provides pair-correlated energy distributions, which allow more stringent tests of energy transfer mechanisms. We find that product state distributions in the dimers are usually non-statistical, and QCT calculations using accurate full dimensional PESs are in accord with and help to elucidate the experiments. A recent joint experimental-theoretical study of the VP dynamics of the water trimer following excitation of the hydrogen bonded OH-stretch fundamental examined the (H2O)3—— H2O + (H2O)2 dissociation channel, which shows statistical product state distributions. Comparing the dissociation energies of the dimer and trimer allows us to place the contribution of non-pairwise additivity to the hydrogen bonding in the trimer. Recent results on the dissociation of the HCl trimer will also be presented. L.C. Ch' ng, A.K. Samanta, G. Czako, J.M. Bowman, H. Reisler, J. Am. Chem. Soc. 134, 15430 ­ 15435 (2012); L.C. Ch'ng, A.K. Samanta, Y. Wang, J.M. Bowman, H. Reisler, J. Phys. Chem. A (in press 2013).

O36 Isomers and Isomerizations in Tropospheric Chemistry: Opening the Black Box of Criegee Intermediate Reactions

Oliver Welz,1 John D. Savee,1 Craig A. Taatjes,1 Arkke J. Eskola,1 Adam M. Scheer,1 Dudley E. Shallcross 2 Brandon Rotavera, 1 EdmundP. F. Lee,3’4 John M. Dyke,3 DanielK. W. Mok, 4 Carl Percival,5 and David L. Osborn 1

1 Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551, USA 2 School of Chemistry, University of Bristol, Bristol BS8 ITS, UK 3 School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK 4 Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 5 School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK Ozonolysis is one of the most important removal mechanisms of unsaturated hydrocarbons in the troposphere. The key intermediate in this pathway is a carbonyl oxide, also known as a “Criegee intermediate ” after Rudolph Criegee, who first proposed their existence in 1949. Since then, many experiments have explored Criegee chemistry, but always through indirect methods, because until 2008 no gas-phase Criegee intermediate (CI) had ever been detected. Two recent breakthroughs have dramatically altered this situation. First, we discovered that the reaction of iodoalkyl radicals (e.g., CH2I) with O2 is a facile method for creating sufficient quantities of carbonyl oxides so that their reactivity can be measured. Second, time-resolved multiplexed photoionization mass spectrometry (MPIMS) allows us to verify the isomeric identity of each CI, while simultaneously probing the time profiles of reactant decay and product formation. Using this approach we have studied the reactions of the two smallest carbonyl oxides, CH2OO (formaldehyde oxide) and CH3CHOO (acetaldehyde oxide) with SO2, NO2, NO, H2O, and carbonyl compounds. In some cases, the directly measured rate coefficients are 104 - 105 times larger than used in recent tropospheric models. The directly measured rates imply a substantially greater role of carbonyl oxides in tropospheric sulfate and nitrate chemistry than previously thought. In this talk I will present an overview of gas phase CI chemistry, including our recent observation that the two conformers of acetaldehyde oxide (syn- and anti-) have dramatically different reaction rates with H2O and SO2. I will also discuss the surprising dynamics of the reactions CI + SO2, in which the reaction is rapid despite the fact that both reactants are singlet molecules.

O37 Photodissociation Dynamics the Simplest Criegee Intermediate CH2OO and its Laboratory Precursor CH2I2

Julia H. Lehman, Hongwei Li, and Marsha I. Lester

Department of Chemistry, University of Pennsylvania Philadelphia, PA 19104-6323

In the troposphere, ozonolysis of alkenes produces Criegee intermediates, which have eluded direct detection until very recently.6-7 In the laboratory, an alternate synthetic route CH2I2 + 248 nm ^ CH2I + I/I* CH2I + O2 ^ CH2OO + I is utilized to produce the simplest Criegee intermediate CH2OO. This study characterizes the 248 nm photolysis of the CH2I2 precursor as well as the dissociation dynamics of CH2OO following UVA excitation on the very strong B 1A' ^ X 1A' transition, nominally a k*^k transition associated with the 4 k e~ COO group. In both cases, the photodissociation dynamics are investigated using velocity map ion imaging (VMI). Upon 248 nm photolysis of CH2I2, the speed and angular distributions of the I* photofragments are obtained using 2+1 resonance- enhanced multiphoton ionization (REMPI). The angular distribution of the I* fragments differs from that anticipated for an excited state with A1/B2 character, suggesting a dissociation process involving multiple electronic states. The energy partitioning shows that the CH2I fragment is produced with a high degree of internal excitation (~36 kcal mol-1), corresponding to ~85% of the available energy, and suggests that the Criegee intermediate will be generated with a similarly high degree of internal excitation in a near thermo-neutral reaction. The CH2OO intermediate is collisionally stabilized and cooled prior to UVA excitation in the 300-360 nm region. UVA excitation results in direct dissociation and yields O(1D) products that are detected using 2+1 REMPI. The velocity distribution of the O(1D) atoms reveals internal excitation of the H2CO cofragment, consistent with theoretical modeling of the dissociation process. The O(1D) angular distribution confirms the B 1A' character of the excited electronic state of CH2OO. Importantly, the present results demonstrate that UVA solar photolysis of the simplest Criegee intermediate yields O(1D) products that will rapidly react with H2O in the troposphere and generate secondary OH radicals.

1 J. M. Beames, F. Liu, L. Lu, and M. I. Lester, J. Am. Chem. Soc. 134 (49), 20045 (2012). 2 O. Welz, J. D. Savee, D. L. Osborn, S. S. Vasu, C. J. Percival, D. E. Shallcross, and C. A. Taatjes, Science 335 (6065), 204 (2012).

O38 Reaction dynamics and kinetics of oxygen isotope exchange reactions: Insights into unusual isotope effects and their applications in earth and planetary science

Kristie A. Boering

Departments of Chemistry and of Earth and Planetary Science, University of California, Berkeley, California, 94720-1460 USA The chemical physics of the unusual quantum symmetry-driven kinetic isotope effects in the ozone formation reaction remain unexplained and, in turn, whether or not similar isotope effects may occur in other chemical systems important in atmospheric and combustion chemistry and earth history. I will give an overview of crossed beam results for the oxygen isotope exchange reactions for O+O2, O+CO2, O+CO, and O+NO2, performed in collaboration with Professors Jim Lin and Y.T. Lee at the Institute for Atomic and Molecular Science, Academia Sinica, Taiwan, as well as results from recent bulk photochemical kinetics experiments for O3 and CO2. The dynamics and kinetics explored for these reactions provide new insights into the "non-mass-dependent" isotope effects in ozone formation, their relationship to the "non-mass-dependent" oxygen isotope compositions of other species such as CO2, CO, and NO and NO2, and possible analogies to the isotopic compositions of species made up of other elements besides oxygen with multiple stable isotopes, such as sulfur. These non-mass-dependent isotopic compositions have diverse biogeochemical and paleoclimate applications, and a better understanding of their chemical physics will provide a sounder foundation for their use as tracers in the environment.

O39 Hyperthermal Scattering of Atomic Oxygen and Argon from a Hot Carbon Surface

Vanessa J. Murray, Tino J. Woodburn, Sridhar A. Lahankar, and Timothy KMinton

Department of Chemistry and Biochemistry Montana State University Bozeman, MT59717 USA [email protected]

Carbon-based materials are utilized as thermal protection systems for hypersonic vehicles in re-entry due to their superior ablation characteristics that lead to efficient heat dissipation. These materials must function at extreme temperatures and oxidizing conditions. The current computational models available fail to predict nonequilibrium gas-surface reactions that heat and ablate surfaces. Atomic oxygen reactions with vitreous carbon provide an experimental model for the ablation chemistry that occurs at the gas-surface interface of the boundary layer during hypersonic flight, which can be used to further refine the existing models. Experimental studies have been conducted on the scattering of atomic oxygen from a model vitreous carbon surface that was resistively heated to temperatures in the temperature range of 800 K to 2000 K, and the dynamics of O-atom scattering have been compared to those for Ar scattering from the same surface. Beams of O and Ar atoms were directed at the hot surface, and angular and translational energy distributions were obtained for inelastically and reactively scattered species by means of a rotatable mass spectrometer detector. Ar and O atom collisions on the surface had incidence energies of 8 eV and 5.2 eV, respectively. The beams struck the surface with incidence angles of 30°, 45°, and 60° with respect to the surface normal. Inelastically scattered O atoms exhibited both thermal and non-thermal components. An increasing fraction of thermally scattered O atoms was observed as the sample temperature was increased. Reactions at the surface yielded molecular oxygen (O2), carbon monoxide (CO), and carbon dioxide (CO2). O2 was formed through two mechanisms: a direct Eley-Rideal mechanism and a thermal mechanism. Scattered CO and CO2 left the surface with a Maxwell-Boltzmann (MB) distribution of velocities described by the surface temperature, indicating a thermal reaction mechanism. As the temperature was increased, the amount of CO produced increased while the amount of CO2 decreased, suggesting that CO left the surface before it could react further to CO2. The amount of CO produced reached a maximum at 1400 K and decreased with increased temperature, probably due to the importance of surface sublimation at high temperatures. Ar is a non-reactive projectile that allows for the investigation of the effect of the high surface temperatures on the scattering dynamics in the absence of a strong interaction potential that allows for several reactive pathways. Inelastically scattered Ar was found to have only non- thermal components. The absence of thermally scattered Ar from the surface indicates that the thermal scattering of atomic oxygen from the surface is likely the result of its strong interaction with the surface.

P1 Reactions of Oxygen with Small Carbon Clusters

Brooks C. Marshall, Sridhar A. Lahankar, and Timothy K. Minton Department of Chemistry and Biochemistry Montana State University Bozeman, MT 59717 USA [email protected]

Mausumi Ray, Biswajit Saha, and George C. Schatz Department of Chemistry Northwestern University 2145 Sheridan Rd. Evanston, IL 60208 [email protected]

Small carbon species such as C, C2, and C3 are not naturally abundant in the Earth’s atmosphere, but are universal transient species in hydrocarbon combustion. They can also be produced from carbon based materials that are used in harsh oxidizing environments, such as thermal protection systems used on re-entry vehicles. The highly exothermic reactions of small carbon species with oxygen atoms and molecules are not well characterized. A better understanding of these reactions will provide insight into reactions of carbon based materials. We have begun experimental studies of the reaction, C + O2 -> CO + O. Carbon atoms are produced by laser ablation of amorphous graphite at 355 nm, and the plume that is produced is entrained in a beam of O2 seeded in a rare gas. The laser ablation of graphite produces a mixture of C, C2, and C3, but the dominant species in the beam is atomic carbon. CO products are detected either mass spectrometrically, or by resonance enhanced multiphoton ionization (REMPI). REMPI allows for quantum state specific detection of CO which is observed in a large range of rovibrational states. We have explored the effects of laser fluence and carrier gas identity on the overall production and the internal energy distribution of CO. The results from these experiments can be compared to theoretical results. Theoretical calculations have been carried out based on quasiclassical trajectory methods with DFT or semiempirical potential surfaces. Trajectory surface hopping methods have been included to account for excited state dynamics and spin-orbit interactions. In addition to the reaction of C with O2, theoretical calculations have also been carried out on the reactions of atomic oxygen with C2 and C3. CO is the dominant product of all the reactions studied, and large fractions of available energy (~40- 50%) may go into vibrational excitation of the CO product.

P2 Dynamics of Hyperthermal Collisions of 16 O(3P) with 18O18O(3Zg ) and N(4^) with D2.

Sridhar A. Lahankar,1 Jianming Zhang, 1 Timothy K. Minton,Gyorgy Lendvay,2 Richard Dawes,3 Jon Camden,4 Hua Guo5 department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA 2Institute of Materials and Environmental Chemistry, Research Center for Natural Sciences, Hungarian Academy of Sciences, Pusztaszeri ut 59-67, H-1025 Budapest, Hungary 3 Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, USA 4 Department of Chemistry, University of Tennessee-Knoxville, Knoxville, TN 37996, USA 5Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM 87131, USA

The atom exchange reaction, 16 O(3P) + 18O18O(3Zg-) ^ 16 O18O + 18O(3P), has been studied at a hyperthermal collision energy, Ecoll, of 86 kcal mol-1, using crossed-molecular-beams experiment and quasiclassical trajectory calculations (QCT). The inelastically scattered 16 O and reactively scattered 16 O18O products were detected with a rotatable mass spectrometer employing electron-impact ionization. The inelastically scattered 16 O atoms scattered sharply in the forward direction relative to the reagent 16 O atoms. The majority of the available energy was partitioned into translation ( = 91%). The 16 O18O products were scattered in the forward and sideways directions relative to the reagent 16 O atoms, indicative of reactive collisions at large impact parameters. The collision energy is partitioned broadly between translational and internal degrees of freedom, with an average of 57% going into translation. QCT calculations were carried out on the ground state singlet potential energy surface. The calculations provide details on the internal excitation of the 16 O18O product. This product may be highly rotationally excited up to j" ~ 150 and highly vibrationally excited up to v" ~ 15.

The reaction of nitrogen and hydrogen, N(4S) + D2 ^ ND(X3E-) + D, has been studied both experimentally in crossed-beams experiments and theoretically with quantum scattering calculations performed on a potential energy surface calculated using MRCI. An experimental excitation function was derived from an experiment with mass spectrometric detection of the ND product, with Ecoll in the range of 21 to 35 kcal mol-1. Experiment and theory are consistent with a reaction barrier of ~28-29 kcal mol-1. Quantum state resolved dynamics of the reaction were investigated using time-sliced velocity map imaging, with Ecoll between 35 and 41 kcal mol-1, where the ND(X3Z-) product was detected using (2+1) REMPI via the D state. Imaging experiments show that the ND(X3Z-) product is predominantly backward scattered relative to the reagent N(4S) atoms. Rotational excitation of product ND(X3Z-) up to j" = 8 was investigated.

P3 Control of chemical reactivity through spatial separation of molecular conformations

D.Rosch1*, S.Willitsch1, Y.-P. Chang 12, J.Kupper2,3

department Chemie, Universitat Basel, 4056 Basel, Switzerland, 2Center of Free-Electron Laser Science, DESY, 22607 Hamburg, Germany, 3 Department4 5 of Physics, University of Hamburg, 22761 Hamburg, Germany. *E-mail: [email protected]

Many molecules have multiple conformations (rotational isomers), which can exhibit different reactivities, opening up perspectives to manipulate chemical reactions by selecting specific molecular conformations [1]. However, a detailed understanding of the role of conformations in gas-phase chemical reactions still has to be established. Here, we present a new technique for the study of reactive collisions between conformer-selected neutral molecules [2] and Coulomb crystals of laser-cooled Ca+ ions [3], which enables to explore the conformation dependence of bimolecular reactions.

The reaction of 3-aminophenol with Coulomb-crystallised Ca+ ions was chosen as a model system. 3-Aminophenol exhibits two different conformations (cis and trans) with different permanent electric dipole moments. Their interaction with external inhomogeneous electric fields enables the two conformers to be spatially separated in a molecular beam passing through an electrostatic deflector [2]. Coulomb-crystals of spatially localised Ca+ ions stored in an ion trap [3] provide a suitable stationary target for the conformer-selected molecular beams enabling the study of conformer-specific reactive collisions with extremely high sensitivities down to the level of single reaction events.

The experimental realization was developed in two stages. First, a molecular-beam machine with an electrostatic deflector was built [2], and the spatial separation of cis- and trans-3-aminophenol seeded in He or Ne was characterized. Subsequently, the molecular-beam apparatus was combined with an ion trap for the generation of spatially localized ensembles of laser-cooled Ca+ ions (“Coulomb-crystals”) [3,4]. By tilting the molecular-beam assembly mechanically, conformationally pure components of the molecular beam have been overlapped with the spatially localised ions in the collision region. The progress of the reaction was monitored by imaging the laser-induced fluorescence of unreacted ions.

The observed rate constant for cis-3-aminophenol is a factor of 2 larger than the one measured for the trans-3-aminophenol. These results agree well with the results from adiabatic capture theory calculations [5]. This agreement indicates that the dynamics of the reaction of Ca+ with cis/trans-3-aminophenol are mainly controlled by the conformer-specific differences in the long- range ion molecule interaction potential.

[1] F. Filsinger, U. Erlekam, G. von Helden, J. Kupper, and G. Meijer, Phys. Rev. Lett. 100, 133003 (2008) [2] F . F ilsing er, J . Kupper, G. Meijer, J. L. Hansen, J. Maurer, J. H. Nielsen, L. Holmegaard, and H. Stapelfeldt, Angew. Chem. Int. Ed. 48, 6900 (2009). [3] S. Willitsch, Int. Rev. Phys. Chem. (2012) [4] F. H. J. Hall, M. Aymar, N. Bouloufa-Maafa, O. Dulieu, S.Willitsch, Phys. Rev. Lett. 107, 243202 (2011) [5] D.C. Clary, J. Chem. Soc. Faraday Trans. 88, 901 (1992)

P4 Rotationally inelastic scattering of CD3 and CH3 with He: comparison of velocity map­ imaging data with quantum scattering calculations

Ondrej Tkac, Alan G. Sage, Stuart J. Greaves and Andrew J. Orr-Ewing School of Chemistry, University of Bristol, Cantock ’s Close, Bristol BS8 ITS, UK

Paul J. Dagdigian 1), Qianli Ma1) and Millard H. Alexander2 1 Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218-2685, USA 2Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2021, USA

Inelastic scattering of the methyl radical is of astrophysical importance since it has been observed in the interstellar medium and in the atmospheres of Saturn1 and Neptune.2 Differential cross sections (DCSs) for rotationally inelastic scattering of CD3 and CH3 radicals with He have been measured at a collision energy of 440 cm-1, using a new miniature crossed molecular beam machine with velocity map-imaging detection.3 We believe that our results are the first DCS measurement for inelastic scattering of a polyatomic free radical. The extracted DCS’s for the CD3+He system are compared with theoretical predictions (see two examples in Fig. 1) calculated from accurate quantum close-coupling calculations based on a PES determined at the CCSD(T) level of theory.4 Excellent agreement between theoretical and experimental DCSs is found for all measured final states with J = 2 - 9. Because we are unable to resolve fully the electronic spectrum of the methyl radical; the DCSs are resolved in J, but averaged over several K projection levels.

Fig. 1. Experimental (red) and theoretical (black) DCSs for the inelastic scattering of CD3 by He, with the inset showing the experimental velocity map images.

References 1. B. Bezard, H. Feuchtgruber, J. I. Moses and T. Encrenaz, A & A 334 (2), L41-L44 (1998). 2. B. Bezard, P. N. Romani, H. Feuchtgruber and T. Encrenaz, Astrophys. J. 515 (2), 868­ 872 (1999). 3. A. Eppink and D. H. Parker, Rev. Sci. Inst. 68 (9), 3477-3484 (1997). 4. P. J. Dagdigian and M. H. Alexander, J. Chem. Phys. 135 (6) (2011).

P5 Progress toward OH-Rb Cold Collisions

Travis C. Briles, Yomay Shyur, Heather J. Lewandowski

JILA/University of Colorado-Boulder

At energies below 1K, molecular collisions enter a quantum regime where the interactions are governed by long-range interactions and threshold behavior. Experiments in this regime are of fundamental interest as they promise to elucidate the quantum nature of reaction dynamics. We present progress towards study of cold collisions of laser-cooled Rb

(T ~ 600uK) and stark decelerated OH radicals (T~100mK) in a co-trapped environment.

We propose to determine the elastic collision cross-section by measuring the time-dependent density distribution in the trap and the inelastic cross-section by measuring the number of molecules lost from the trap as a function of time. The OH radicals are detected through a new 1+1’ REMPI scheme [1] , which exploits the highly sensitive nature of ion detection .

This feature should be especially advantageous over LIF in a co-trapped environment that suffers from very small photon collection efficiencies. 1

[1] Jospeh M. Beames, Fang Liu, Marsha I. Lester, and Craig Murray, Communication: A new spectroscopic window on hydroxyl radicals using UV+VUV resonant ionization, The

Journal of Chemical Physics, 134, 241102 (2011)

P6 New Developments in the Electron Nuclear Dynamics Method: From Coherent-States and Density-Functional-Theory Implementations to Applications in Cancer Proton Therapy

S. Ajith Perera1 and Jorge A. Morales 2

department of Chemistry, Quantum Theory Project, University of Florida, Gainesville, FL

32611, 2Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409.

The electron nuclear dynamics (END) method [1, 2] is a time-dependent, variational, and non- adiabatic approach to chemical dynamics that employs no predetermined potential energy surfaces. END dynamical equations are obtained through the time-dependent variational principle applied to trial total wavefunctions in the coherent-state (CS) representation [1, 2]. Unlike Ehrenfest methods, END contains non-adiabatic coupling terms to achieve appropriate electron-nuclear descriptions [3]; unlike Born-Oppenheimer dynamics methods, END is not confined to the electronic ground state and can describe electron excitations and transfers. The simplest-level END (SLEND) [1,2] treats nuclei in a classical-mechanics fashion (as the zero- width limit of nuclear wave packets) and electrons with a single-determinantal wavefunction. Starting with SLEND, three interrelated developments will be discussed: (1) The use of different types of CSs [2, 4, 5] to describe all types of particles (nuclei and electrons) and of degrees of freedom (translational, rotational [2], vibrational -harmonic [6 ,7] and anharmonic [8]- and electronic [1, 2]). Rotational and vibrational CSs reconstruct quantum excitation probabilities from the SLEND nuclear classical dynamics. The electronic Thouless CS [1,2] provides an appropriate parameterization for the electronic wavefunction, and another electronic CS from the valence bond theory [5] renders a charge-equilibration model based on the Sanderson principle of electronegativity equalization; (2) the new SLEND/Kohn-Sham-density-functional-theory [9] and END/coupled-cluster-theory (under development) methods; and (3) our parallel codes PACE and PACE/ACESS III implementing the present models. While those models can describe various reactions [1, 2], we will mainly illustrate them in their novel application to several proton cancer therapy reactions, such as water radiolysis reactions and damage processes on DNA components. [1] E. Deumens, A. Diz, R. Longo, Y. Ohrn, Rev. Mod. Phys., 66 (1994) 917-983. [2] C. Stopera, T.V. Grimes, P.M. McLaurin, A. Privett, J.A. Morales, Adv. Quant. Chem., in Press, (2013). [3] R. Longo, A. Diz, E. Deumens, Y. Ohrn, Chem. Phys. Lett., 220 (1994) 305-311. [4] J.A. Morales, Mol. Phys., 108 (2010) 3199-3211. [5 ] J.A. Morales, J. Phys. Chem. A, 113 (2009) 6004-6015. [6] C. Stopera, B. Maiti, T.V. Grimes, P.M. McLaurin, J.A. Morales, J. Chem. Phys., 134 (2011) 224308. [7] C. Stopera, B. Maiti, T.V. Grimes, P.M. McLaurin, J.A. Morales, J. Chem. Phys., 136 (2012) 054304. [8] C. Stopera, B. Maiti, J.A. Morales, Chem. Phys. Lett., 551 (2012) 42-49. [9] S.A. Perera, P.M. McLaurin, T.V. Grimes, J.A. Morales, Chem. Phys. Lett., 496 (2010) 188.

P7 Helium Nanodroplet Isolation Spectroscopy and ab initio Computations of HO3-(O2)n

Clusters (n=0-4)

Tao Liang, Paul Raston, and Gary E. Douberly

Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA

The hydridotrioxygen radical (HOOO) and its deuterated analog have been isolated in helium nanodroplets following the in-situ association reaction between OH and O2. The infrared spectrum in the 3500-3700 cm-1 region reveals bands that are assigned to the u1 (OH stretch) fundamental and u1+ u6 (OH stretch plus torsion) combination band of the trans- HOOO isomer. The helium droplet spectrum is assigned on the basis of a detailed comparison to the infrared spectrum of HOOO produced in the gas phase [E. L. Derro, T. D. Sechler, C. Murray, and M. I. Lester, J. Chem. Phys. 128, 244313 (2008)]. Despite the characteristic low temperature and rapid cooling of helium nanodroplets, there is no evidence for the formation of a weakly bound OH-O2 van der Waals complex, which implies the absence of a kinetically significant barrier in the entrance channel of the reaction. There is also no spectroscopic evidence for the formation of cis-HOOO, which is predicted by theory to be nearly isoenergetic to the trans isomer. Stark spectroscopy of the trans-HOOO species provides vibrationally averaged dipole moment components that qualitatively disagree with predictions obtained from CCSD(T) computations at the equilibrium, planar geometry, indicating a floppy complex undergoing large-amplitude motion about the torsional coordinate. A two-dimensional vibrational Hamiltonian has been derived, and bound state calculations on a CCSD(T)/Def2-TZVPD potential surface are carried out with a discrete variable representation method. The vibrationally averaged dipole moment components for trans-HOOO obtained in this way are in reasonable agreement with experiment. Under conditions that favor the introduction of multiple O2 molecules to the droplets, bands associated with larger H/DOOO-(O2)n clusters are observed shifted ~1-10 cm-1 to the red of the trans-H/DOOO u1 bands. Detailed ab initio calculations are carried out for multiple isomers of cis- and trans-HO3-O2, corresponding to either hydrogen or oxygen bonded van der Waals complexes. Comparisons to theory suggest that the structure of the HO3-O2 complex formed in helium droplets is a hydrogen-bonded 4A' sp ecies consisting of a trans- HO3 core. The computed binding energy of the complex is approximately 240 cm-1. Despite the weak interaction between trans-HO3 and O2, non-additive red shifts of the OH stretch frequency are observed upon successive solvation by O2 to form the larger clusters with n>1, perhaps indicating aggregation induced trans to cis isomerization. Does Ozone-Water Complex Produce Additional OH Radicals in the Atmosphere?

Bing Jin,1 Man-Nung Su,1 and Jim Jr-Min Lin* 1,2,3

1Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 10617 ^Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan 30010 3Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617 E-mail: [email protected]

For decades, the photolysis of O3-H2O complex in the near UV region (~350 nm)1 has been regarded as an additional source of atmospheric OH radicals (O3-H2O + hv^ - 2 OH + O2).12 From the experimental point of view, it is difficult to study this weakly bound complex. First, the conventional optical absorption method hardly rules out the contribution of contaminations (e.g., higher clusters, O3 and H2O monomer and other impurities).3 Second, the binding energy of the ozone-water complex is very small and unknown.2,3 Finally, the ozone/water mixture is quite corrosive even to the stainless steel materials.4 In this work, a newly designed dual-pulsed-valve assembly was utilized to produce O3-H2O complexes (Fig. 1).4 With argon solvation and photoionization5 by tunable vacuum UV light from a synchrotron radiation (Taiwan Light Source), we were able to selectively probe the ozone-water 1:1 complex. We used a mass- selected laser-depletion method6 to determine the absorption cross section of the complex without suffering from the interferences of other species. The cross section was examined at 157.6, 248.4, 308.4 and 351.8 nm (Fig. 2).4 At 351.8 nm, the absorption of the ozone-water complex was not observed (Fig. 2), indicating its cross section is much smaller than previously thought. Based on our new data, the OH production from the photolysis of this complex would be insignificant in the troposphere. 4

O3/Ar Pulsed Valve Laser Quadrupole Mass Filter Li K MolecuMo, lar Beam Detector 1

HO/Arn n Slit y Pulsed Valve Synchrotron Radiation

Fig. 1. Experimental schematic (not to scale). Fig. 2. Photodepletion signals at 248, 308 and 352 nm.

[1] Y. Hurwitz and R. Naaman, J. Chem. Phys., 102, 1941 (1995). [2] G. J. Frost and V. Vaida, J. Geophys. Res., 100(D9), 18803 (1995). [3] V. Vaida, J. Chem. Phys, 135(2), 020901 (2011). [4] Bing Jin, Man-Nung Su, and Jim Jr-Min Lin, J Phys. Chem. A, 116, 12082 (2012). [5] Amir Golan and Musahid Ahmed, J. Phys. Chem. Lett., 3 (4),458 (2012). [6] H.-Y. Chen, C.-Y. Lien, W.-Y. Lin, Y. T. Lee, and J. J. Lin, Science, 324, 781 (2009).

P9 Inelastic collision rates of ortho-H2O molecules with Helium atoms at 100 K

S. Montero 1, G. Tejeda1, J. M. Fernandez1, E. Moreno 1, E. Carmona2, andM. Hernandez2

[email protected]

laboratory of Molecular Fluid Dynamics, IEM, 2 Instituto de Flsica Fundamental,

CSIC, Madrid, Spain

An experimental method for the study of inelastic collisions within the vibrational ground state will be reported. The method is based in the production, spectroscopic measurement (Raman), and quantitative analysis of flow data in H2O+He supersonic jet mixtures. The primary experimental data are number densities and rotational populations which are then reduced to rotational, translational temperatures, and flow velocities. From these data the time evolution of rotational populations of H2O along the supersonic jets is determined with accuracy up to 1 %. The analysis of time evolution by means of a kinetic Master Equation permit us obtaining the H2O:H2O and H2O:He average rate coefficients associated to each rotational level. Employing the relative values from some ab-initio state-to-state rates as starting values, in combination with the H2O:H2O self-collision average rates, the experimental state-to-state rate coefficients for H2O:He inelastic collisions are obtained.

The method is applied here in detail to the state-to-state rates for collisions of ortho -H2O molecules with helium atoms at 100 K. In the experiment the data from six independent H2O+He supersonic jets with different proportions of helium permit us obtaining the rates for the eight lowest rotational levels of ortho-H2O with accuracy better than 10% for the dominant processes. Ab-initio rates from two different H2O-He potential energy surfaces (PES) [1-3] will be compared with the experiment. Conclusions about the quality of the respective PESs will be discussed.

Broadening coefficients of some rotation lines of ortho -H2O in the THz region, which have been calculated from the inelastic rates reported in this work, will be compared with independent spectroscopic results [4].

References

[1] S. Maluendes, A. D. McLean, and S. Green, J. Chem. Phys. 96, 8150 (1992). [2] S. Green, S. Maluendes, and A. D. McLean, Astrophys. J. Suppl. Ser. 85, 181 (1993). [3] M. P. Hodges, R. J. Wheatley, and A. H. Harvey, J. Chem. Phys. 116, 1397 (2002). [4] M. J. Dick, B. J. Drouin, and J. C. Pearson, Phys. Rev. A81, 022706 (2010).

P10 Towards fully state-resolved reaction probabilities of sixatom reactions

Ralph Welsch1, Uwe Manthe1

1 Theoretische Chemie, Universitat Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany Electronic mail: [email protected]

Flux correlation functions facilitate the efficient computation of reaction rates and initial state- selected reaction probabilities. Recent theoretical development extended their applicability to the calculation of state-to-state reaction probabilities [1,2]. Full-dimensional quantum dynamics calculations employing the multiconfigurational time-dependent Hartree (MCTDH) approach can be used to obtain reaction probabilities for six atom reactions.

The H + CH4 ^ H2 + CH3 reaction is studied as benchmark example. The full-dimensional state- resolved computations are numerically very demanding. Since time-dependent grids are used to evaluate the MCTDH potential energy matrix elements, the evaluation of the potential energy surface (PES) is the most time consuming step of the calculation. Thus, the first full-dimensional initial-state selected calculations could only employ the simple but inaccurate Jordan-Gilbert PES [3,4].

Here, full-dimensional state-resolved calculations for the H + CH4 ^ H2 + CH3 reaction on an accurate Shepard interpolated PES will be presented. The multi-layer extension of the MCTDH approach provides an increased efficiency of the quantum dynamics calculations compared to Refs. [3,4]. Furthermore, the architecture of modern graphics processing units (GPUs) is used to speed up the evaluation of the potential energy surface (PES) and an efficient scheme to enhance the evaluation of Shepard interpolated PES is employed [5].

First results on initial state-selected reaction probabilities of H + CH4 ^ H2 + CH3 on a new and accurate PES will be presented and the extension to state-to-state calculations will be discussed.

[1] Welsch, R., Huarte-Larranaga, F., Manthe, U., J. Chem. Phys. 136 64117 (2012) [2] Welsch, R. and Manthe, U., Mol. Phys. 110 703 (2012) [3] Schiffel, G. and Manthe, J. Chem. Phys. 132 191101 (2010) [4] Schiffel, G. and Manthe, J. Chem. Phys. 133 174124 (2010) [5] Welsch, R. and Manthe, J. Chem. Phys. 138 164118 (2013)

P11 Resonance excited states energies and life-times: Suite of complex scaled EOM-CCSD methods Dmitry Zuev, Ksenia B. Bravaya, Anna I. Krylov University of Southern California, Los Angeles, CA

Resonance states are ubiquitous in Nature: they encounter in atomic and molecular systems, in plasma and in radioactive isotopes. We present a new suite of ab initio methods for calculation of autoionizing electronically excited states (both positions and lifetimes) - complex scaled equation-of-motion coupled-cluster (cs-EOM-EE-CCSD and cs-EOM-EA-CCSD) theories combined with complex scaled coupled cluster (cs-CCSD) and complex scaled Hartree-Fock (cs- HF). The problem in description of this phenomenon lies in the exponentially divergent character of the resonance wave-function. These states can not be described using conventional ab initio methods and special techniques have to be used. An elegant solution is provided by complex scaling formalism in which resonance wave-function is naturally obtained as a square-integrable eigenfunction of the complex-scaled Hamiltonian, and real and imaginary parts of the complex eigenvalue correspond to the resonance position and life-time, respectively [1-3]. This technique enables description of the resonance states with the same methods and algorithms one usually uses to describe bound states. We present an implementation of the cs-EOM-EE-CCSD and cs- EOM-EA-CCSD methods, which combine ideas of the complex scaling method for treating resonance states with state-of-the-art quantum chemistry description of the excited states and electron-attached states (EOM-EE-CCSD and EOM-EA-CCSD, [4]). Ground state obtained by cs-HF and cs-CCSD is a suitable reference for cs-EOM-CCSD calculations. Our test calculations of atomic resonances on two (H-, He) and many electron (Be) systems give accurate values of both resonance position and lifetime [5-6]. The methods can be universally applied to both Feshbach and shape type of resonances. 1

1. Moiseyev N., Non-Hermitian quantum mechanics. Cambridge University Press (2011). 2. Reinhardt W.P., Annu. Rev. Phys. Chem. 33, 223 (1983). 3. Moiseyev N., Phys. Reports 302, 211 (1998). 4. Sinha et al., CPL 129, 369 (1986). 5. Ho Y.K., Bhatia A.K., and Temkin A., Phys. Rev. A 15, 1423 (1977). 6. Lindroth A., Phys. Rev. A 49, 4473 (1994).

P12 Investigation of HCCCO2" and "CCCO2H by Photoelectron-Photofragment

Coincidence Spectroscopy

Amelia W. Ray, Rico Otto, Jennifer Daluz, and Robert E. Continetti

Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La

Jolla, CA 92093-0340, USA

Carboxyl free radicals are known to play an important role in organic synthesis as well as in oxidation and combustion processes. The work presented here extends our previous studies of the dissociation dynamics of carboxyl free radicals to the propiolyl radical (HCCCO2) and the related isomer CCCO2H. To this aim, the dissociative photodetachment of HCCCO2 and the photodetachment of the carbanion, CCCO2H, where investigated using photoelectron-photofragment coincidence spectroscopy. The HCCCO2 anion was found to readily dissociate to HCC + CO2 upon photodetachment at hv = 4.80 eV. The kinetic energy release spectrum for the HCC + CO2 products shows resolved excitation of the OCO bend of the CO2 fragment, similar to our previous studies of HCO2 ——H + CO2. At this wavelength it was determined that there are no energetically allowed dissociation pathways for the neutral CCCO2H isomer. We are currently carrying out appropriate ab initio calculations for the anionic and neutral surfaces, including relevant isomerization and dissociation barriers, to aid in the interpretation of these results. This work was funded by the United States Department of Energy, under grant number DE-FG03-98ER14879.

HCCCO2 Syn-CCCO2H

P13 Dissociative Photodetachment of Vibrationally Excited F (H2O)

Rico Otto, Amelia W. Ray, Jennifer Daluz, and Robert Continetti

Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, 92093 CA, USA

The four atom reaction F + H2O ^ HF + OH has the potential for becoming a new benchmark reaction for polyatomic reaction dynamics. Experimental studies focused on probing product state distributions for this system have revealed complex dynamics, including significant non-adiabatic effects.1 Recently, a full dimensional quantum dynamical treatment of this 19- electron system was carried out, providing motivation for further experimental investigation of the reaction dynamics. 2 In our lab we have made use of the dissociative photodetachment of F (H2O) to probe this reaction using photoelectron-photofragment coincidence (PPC) spectroscopy, and we are now seeking to extend these studies by vibrationally exciting the precursor F (H2O) anions prior to photodetachment. These experiments are carried out on a fast beam PPC spectrometer using a cryogenically cooled electrostatic ion beam trap (EIBT) to store the anions during the experiment. Studies of vibrationally excited anions are being pursued using direct absorption of the output of a 10 Hz Nd:YAG-pumped IR OPO/OPA, irradiating the entire ion bunch in a counter-propagating collinear arrangement prior to injection into the EIBT. Starting on the anionic F (H2O) potential energy surface, our aim is to vibrationally excite the nearly linear ionic F-H-O bond near 2900 cm-1.3 Following vibrational excitation, the species is photodetached with a 4.8 eV photon in the EIBT, producing the neutral F(H2O) in the vicinity of the transition state for the neutral bimolecular reaction. Vibrationally exciting the parent anions will allow probing of an extended Franck-Condon region on the neutral F(H2O) potential energy surface, providing a more stringent test of the potential energy surface and reaction dynamics calculations for this reaction. We will be particularly interested in examining the effect of vibrational excitation on the product branching ratios for the reaction. This work was funded by the United States Department of Energy, under grant number DE-FG03-98ER14879.

References 1. A. Zolot, D. Nesbitt, J. Chem. Phys. 129, 184305 (2008) 2. J. Li, R. Dawes, H. Guo, Jour. Chem. Phys. 137, 094304 (2012) 3. A. McCoy, M. Johnson, J. Phys. Chem. A, 112, 12337 (2008)

P14 Cold charge-transfer reactions in Coulomb crystals

Brianna Heazlewood 1, Lee Harper1, Nabanita Deb1, Heather Lewandowski2 & Timothy Softley 1

department of Chemistry, the University of Oxford

2JILA and the Department of Physics, University of Colorado

Reactive collisions between xenon ions and ND3 molecules are examined within a

Ca+ Coulomb crystal. An ion trap is loaded with calcium ions, which are subsequently

Doppler cooled to adopt a “Coulomb crystal” phase (Fig. 1A) . Xenon molecules leaked into

the reaction chamber are subsequently ionised, enabling Xe+ to be sympathetically cooled

into the crystal. The incorporation of Xe+ ions into the crystal is monitored through spatial

changes in the fluorescence emitted by the trapped Ca+ ions, indicated by a flattening of the

observed crystal shape (Fig. 1B). To investigate the charge-exchange reaction between cold, trapped xenon ions and internally cold neutral molecules, a guided molecular beam of ND3 is

introduced to the reaction chamber. ND3+ ions (formed following charge-exchange with Xe+)

are sympathetically cooled into the centre of the Coulomb crystal (Fig. 1C). Changes in the

spatial location of the fluorescing Ca+ ions enable the charge exchange process to be

examined and the rate of reaction calculated. Progress towards examining this reaction with

Stark decelerated (and thus translationally cold) ND3 molecules is also presented.

Figure 1. Experimental (left column) and simulated (right column) images of a Ca+ Coulomb crystal, recorded over the course of a charge exchange reaction between Xe+ and ND3. (A) Ca+ Coulomb crystal; (B) following the incorporation of (heavier, non­ fluorescing) Xe+ ions into the crystal; and (C) after charge exchange between Xe+ and (lighter, non-fluorescing) ND3 molecules.

P15 Rotational Polarisation Effects in the Inelastic Collisions of NO(X) and Ar

B. Hornung, M. BrouardIS §, H. Chadwick1 , C. J. Eyles 1 , B. Nichols 12, F. J. Aoiz , P. G. Jambrina3 ,

M. de Miranda4, Steven Stolte5

1 Department of Chemistry, University of Oxford, OX1 3QZ, Oxford, UK 3'Departmento de Quimica Fisica, Universidad Complutense, Madrid 28040, Spain 3'Departmento de Quimica Fisica, Universidad de Salamanca, Salmanca 37008, Spain 4'School of Chemistry, University of Leeds, United Kingdom, LS2 9JT, Leeds, UK 5 Atomic and Molecular Physics Institute, Jilin University, Changchun 130012, China

The origin of rotational polarisation in the rotationally inelastic scattering of NO(X2n1/2) with Ar has been investigated by means of quantum mechanical, quasi-classical trajectory, and classical Monte Carlo scattering calculations. It has been shown that the repulsive nature of the interaction potential at a collision energy of 65meV is primarily responsible for the rotational alignment, preferred plane of rotation, and it can be well explained in terms of classical impulsive collisions of hard shells [1].

On the contrary, the rotational orientation, or preferred sense of rotation, largely depends on the details of the interaction potential and the parity changing or conserving nature of the collisions. It does not exist in the classical description of hard shell collisions if the system exhibits simple symmetry properties, which will be discussed. The presence of rotational orientation is due to the breakdown of these symmetries.

We first calculated the exact quantum mechanical rotational polarisation in the collisions of hard shells. We found that a hard shell can have a preferred sense of rotation purely due to quantum effects, even in those cases when this is not predicted by classical treatment. This is a fundamental difference between the quantal and classical descriptions of atom-diatom interactions. 1

[1] M. Brouard, H. Chadwick, C. J. Eyles, B. Hornung, B. Nichols, F. J. Aoiz, P. G. Jambrina, S. Stolte, and M. P. de Miranda, J. Chem. Phys. 138, 104309, (2013)

P16 Reaction Coordinates, Bifurcations, and IVR

David S. Perry

The University of Akron, Akron, OH 44325

The potential energy along a unimolecular reaction coordinate is not harmonic, but has a diminshing slope as the saddle point or transition state is approached. In some cases, one of the vibrational normal modes changes smoothly to become the reaction coordinate as the energy increases toward the reaction threshold, but often there are bifurcations in the classical dynamics, and corresponding changes in the quantum dynamics, that result in the formation of a new vibrational mode with motion aligned along the reaction coordinate. The decreasing slope of the p otential along the reaction coordinate causes the frequency of this “reaction mode” to decrease markedly as the energy increases toward the reaction threshold.

The spectroscopic study of reaction modes at or near the reaction threshold1 offers the prospect of studying an incipient reaction in the process of happening and provides a conceptual basis for developing coherent control methodologies. The challenges facing such spectroscopic studies include (a) the difficulty of identifying a relatively small number of reaction mode states among a sea of spectroscopic features, and (b) instabilities that render the reaction mode states short-lived and consequently hard to detect. For the present purposes, we categorize such instabilities as arising from either “systematic” or “accidental ” resonances . “Systematic” resonances couple those modes involved in the relevant bifurcations including the “transition modes” that approach zero (or nearly zero) frequency at the transition state . Examples of systematic resonances include 1:n resonances that lead to higher-order bifurcations in HOCl 12 and rotational l-type resonances in acetylene.3 “Accidental ” resonances involve one or more additional vibrational modes that are not instrinsically part of the reaction process, and may be much weaker than the systematic resonances. An example of accidental resonances is the Coriolis resonances in acetylene that couple the bending modes to the CH and C=C stretches.3 These resonances can give rise to IVR, to energy randomization, and classically, to chaos.4 For the acetylene to vinylidene reactions, the reaction mode is the local bender. Computations based on high resolution spectroscopic data indicate that the local bender is affected by both types of instabilities. The results suggest that passive control of the rotationally mediated instabilities in acetylene by cooling to a low rotational temperature should be effective. 1

1 K. Prozument, R. G. Shaver, M. Ciuba, J. S. Muenter, G. B. Park, J. F. Stanton, H. Guo, B. M. Wong, D. S. Perry, and R. W. Field, A New Approach toward Transition State Spectroscopy, Faraday Discuss. (2013). http://dx.doi.org/http://dx.doi.org/10.1039/C3FD20160K 2 J. Weiss, J. Hauschildt, S. Y. Grebenshchikov, R. Duren, R. Schinke, J. Koput, S. Stamatiadis, and S. C. Farantos, J. Chem. Phys. 112, 77 (2000). http://dx.doi.org/10.1063/L480563 3 D. S. Perry, J. Martens, B. Amyay, and M. Herman, Mol. Phys. 110, 2687 (2012). http://dx.doi.org/10.1080/00268976.2012.711493 4 M. Herman, and D. S. Perry, Phys. Chem. Chem. Phys. 15, 9949 (2013). http://dx.doi.org/http://dx.doi.org/10.1039/C3CP50463H.

P17 Slow photoelectron velocity-map imaging (SEVI) spectroscopy of cold anions

Marissa Weichman, Jongjin B. Kim, and Daniel M. Neumark

Department of Chemistry, University of California, Berkeley, California 94720, USA

Anion slow photoelectron velocity-map imaging (SEVI) spectroscopy is a high- resolution variant of photoelectron spectroscopy used to study the electronic and geometric structure of atoms, molecules, and clusters. Anions are cryogenically cooled in a radio­ frequency ion trap before photodetachment, suppressing hot bands and sequence bands, and yielding peak widths down to 4 cm-1 for molecular systems. Recent spectra of species of interest are presented, including small carbon clusters, polycyclic aromatic hydrocarbons, and transition states of bimolecular reactions.

P18 A New Lookat the Photodissociation of Methyl Iodide at 193 nm

Hong Xu and S. T. Pratt Argonne National Laboratory, Argonne, IL 60439 USA

ABSTRACT The photodissociation of methyl iodide has long provided a benchmark for the dynamics studies of small polyatomic molecules. In particular, photodissociation in the A band between 220 nm and 340 nm has been the subject of numerous experimental and theoretical studies, and a general consensus has been reached on the description of this process. In contrast, considerable discrepancies still exist for the photodissociation of methyl iodide at shorter wavelengths that access the lowest Rydberg states. In particular, measurements for the quantum yield of excited I*( 2P1/2) atoms at 193 nm range from 1.0 to 0.7. To provide insight into this discrepancy, we have performed a new measurement of the photodissociation of CH3I at 193 nm by using a combination of vacuum ultraviolet photoionization and velocity map ion imaging. The I and I* photofragments are probed by single-photon ionization at photon energies above and below the I photoionization threshold. The relative I and I* photoionization cross sections are determined at these wavelengths by using the known branching fractions for the photodissociation at 266 nm. Velocity map ion images show conclusively that the branching fraction for I(2P3/2) atoms is non­ zero, and yield a value of 0.05 ± 0.01. Interestingly, the translational energy distribution extracted from the image shows that the translational energy of the I fragments is significantly smaller than that of the I* atoms. We will show that this observation is consistent with the previous measurements, and can be used to provide a more complete picture of the dissociation dynamics.

The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”) . Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02- 06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

P19 Optical pumping H2 molecules to rovibrationally excited states with

nearly complete population transfer

Wenrui Dong, Nandini Mukherjee and Richard N. Zare

Department of Chemistry, Stanford University, Stanford, California

94305-5080

Using stimulated Raman adiabatic passage (SARP), it is possible, in principle, to transfer all the population in a rovibrational level of an isolated diatomic molecule to an excited rovibrational level. We use an overlapping sequence of pump (532 nm) and dump (683 nm) single-mode laser pulses of unequal fluence to prepare isolated H2 molecules in a molecular beam. Using the Q(0) line of a Raman transition, we have demonstrated that SARP can achieve nearly complete population transfer (97 ± 7 %) from H2(v=0, J=0) to H2(v=1, J=0) state in a beam of H2 molecules. The maximum population transfer was observed for an inter-pulse delay of 5.5 ns which is comparable to the temporal width of the pump laser pulse. A pump laser pulse fluence of ~ 100 J/cm12 3and dump laser pulse fluence of ~ 10 J/cm2 is estimated by theoretical simulation of the experimental results. FWHM of the depletion peak changes with delay and maximizes at the same delay for which the depletion is maximum. Dump laser pulse frequency at the depletion peak can be determined by the Stark-shifted energy difference between the initial and final levels when Rabi frequency reaches its peak value. An explanation is presented of the SARP process and how these results are obtained.

1. N. Mukherjee and R. N. Zare, J Chem Phys 135 (2) (2011). 2. N. Mukherjee and R. N. Zare, J Chem Phys 135 (18) (2011). 3. N. Mukherjee, W. R. Dong, J. A. Harrison and R. N. Zare, J Chem Phys 138 (5) (2013).

P20 A Theoretical Study of Reaction of Ketene with Water in the Gas-Phase:

Formation of Acetic Acid?

Thanh Lam Nguyen,1 Bert C. Xue,1 Barney G. Ellison,2 and John F. Stanton^*

1Department of Chemistry & Biochemistry, The University of Texas at Austin, Austin, TX 78712-0165. 2University of Colorado at Boulder Department of Chemistry and Biochemistry, 215 UCB, Boulder, CO 80309 [email protected] and [email protected]

Abstract:

The gas-phase hydration of ketene by water (uncatalyzed and with an addition catalytic water) to produce acetic acid was theoretically characterized using high-level coupled-cluster methods, followed by a two-dimensional master equation analysis to compute thermal reaction rate constants. The results show that the formation of acetic acid quite likely occurs in high- temperature combustion of biomass, but that the rate for acetic acid formation from ketene is negligible under ambient atmospheric conditions.

kcal/mol

0.0

□32.2 Acetic Acid

P21 Inelastic Scattering of jet cooled NO at Gas-Ionic Liquid Interfaces

Amelia Zutz, David J. Nesbitt

JILA and National Institute of Standards and Technology,University of Colorado, Boulder, CO

The identities of cation and anion species in room-temperature ionic liquids (RTILs)

are varied to explore their effect on collision dynamics at gas-RTIL interfaces. These

interfaces are probed with state-to-state resolved scattering of NO [2n1/2 (J=0.5)] from bmim-

Tf2N, bmim-BF 4, C12mim-Tf2N and C12mim-BF4. A supersonically cooled molecular beam

of NO collides with the surface 45° normal to the surface and scattered molecules are

detected using LIF at a 45° specular angle. The temperature of the surface is varied over a

100° range and the collision energies of the molecular beam are varied from 1 to 20 kcal/mol.

Full quantum state resolution of detected scattered molecules allows for rotational and

electronic (2n1/2 and 2n3/2 spin-orbit states) information to be extracted from the populations

By seeing how different ionic species in RTILs influence rotational and electronic excitation, we can learn more about how the gas-RTIL interface is changed by varied alkyl chain lengths

and anion identities.

P22 Resonance structures in the entrance channel of the F+CH4/CD4 reaction: A quantum

dynamics investigation

Till Westermann, Juliana Palma and Uwe Manthe

Fakultat fur Chemie, Universitat Bielefeld, Germany

F(2P)+CH4 -> HF+CH3 is a benchmark example for a polyatomic reaction. To explore the potential energy surfaces in the vicinity of the reaction barrier, transition state spectroscopy has been employed and highly structured photodetachment spectra were obtained 1 . Due to the high dimensionally, the interpretation of the spectra is not straightforward. Questions whether these structures are the first hints to reactive resonances in six-atom reactions and their connections with steering effects found in initial state selected molecular cross beam experiments could not be answered. This work aims to explain just that. The photodetachment spectrum is simulated on a newly developed, full dimensional (12D), diabatic PES for the F(2P)+CH4 -> HF+CH3 entrance channel. The PES is based on UCCSD(T)-F12 and MRCI (aug-VTZ) ab initio calculations and takes into account for the six relevant electronic states, including spin-orbit interaction via an accurate, analytic Hamiltonian. Full dimensional (12D) quantum dynamics utilizing the multi-configurational time-dependent Hartree approach are carried out taking into account all six electronic states on a picosecond time scale. Highly structured spectra are obtained from the dynamics simulation with progressions that are in good agreement with the experimental high-resolution data. Having analyzed the time- dependent wave function, the spectrum is understood based on periodic orbits. A clear picture of the dynamics in the reactive F(2P)*CH 4 van der Waals complex can be drawn, which will be discussed in detail.

1 T.I. Yacovitch, E. Garand, J. B. Kim, C. Hock, T. Theisa and D. M. Neumark, Farad. Discuss. 157, 399 2012 P23 Molecular dynamics simulations of CO2 formation in interstellar ices

C. Arasa,.f.} M. C. van Hemert.t E. F. van Dishoeck.} and G. J. Kroesf

f Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P. O. Box 9502, 2300RA Leiden, The Netherlands } Leiden Observatory, Leiden University, P. O. Box 9513, 2300RA Leiden, The Netherlands

CO2 ice is one of the most abundant components in ice-coated interstellar dust grains, besides H2O and CO. Yet, the most favorable path to CO2 ice is still not fully clear. Among the three possible routes, HCO + O ^ CO2 + H, CO + OH ^ CO2 + H and CO + O ^ CO2 , the one where a CO molecule reacts with an OH radical is the obvious one when the OH radicals are produced by photodissociation of water molecules. Molecular dynamics calculations on different kinds of CO-H2O ice systems have been performed at 10 K in order to demonstrate that the reaction between CO and an OH radical resulting from H2O photodissociation through the first excited state is a possible and plausible route to form CO2 ice. Our calculations, which take into account different ice surface models, suggest that there is another product with a higher formation probability ((3.00±0.07)*10 -2), which is the HOCO complex, whereas the formation of CO2 has a probability of only (3.6±0.7)x 10-4. The initial location of the CO is key to obtain reaction and form CO2: the CO needs to be located deep into the ice. The HOCO complex becomes trapped in the cold ice surface in the trans-HOCO minimum because it quickly loses its internal energy to the surrounding ice, preventing further reaction to H + CO2. Several laboratory experiments have been carried out recently and they confirm that CO2 can also be formed through other, different routes. Here we compare our theoretical results with the data available from experiments studying the formation of CO2 through a similar pathway as ours, even though the initial conditions were not exactly the same. Our results also show that the HCO van der Waals complex can be formed through the interaction of CO with the H atom that is formed as a product of H2O photodissociation. Thus, the H + CO reaction can be a possible route to form HCO ice and, provided there is a source of atomic oxygen, also to form CO2 ice. Finally it is realized that the bombardment of water molecules with energetic H atoms resulting from the photodissociation process provides an additional source of OH radicals through the H2O + H ^ OH + H2 reaction. This channel was not taken into account in our MD simulations since all water molecules but the dissociating one were treated as rigid rotors. The secondary OH radicals have a translational and rovibrational energy distribution that differs from the primary ones. Consequences will be discussed.

P24 The Collisional Energy Dependence of Hydrogen Abstraction from Stretch Excited CH3D by Chlorine Radicals

Andrew E. Berke, Ethan H. Volpa, Christopher J. Annesley, F. Fleming Crim

Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

By photolyzing Cl2 at three different wavelengths (309 nm, 355 nm, and 416 nm) to produce varying center-of-mass frame collisional energy distributions, we have studied the extent to which translational energy influences the H or D abstraction from CH3D. The results of this study indicate that the barrier to H abstraction is around 1200 cm-1, and that tunneling seems to be entirely responsible for the CH2D signal we see from the ground state reaction at the lowest collision energy. Putting one quantum of stretch excitation into each of two separate C-H oscillators leads to H abstraction enhancement at all collisional energies, but yields no CH2D products in the ground vibrational state. Instead, all CH2D products have retained a quantum of C-H stretch, indicating that the non-reacting bond is a spectator throughout the course of the reaction. At the two higher collisional energies, some of the products carry a quantum of out-of­ plane bend in addition to C-H stretch excitation. Relative intensity differences for certain rovibrational lines in the 416 nm action spectrum vs. those observed in the action spectra taken at the two higher photolysis energies may suggest the existence of a shallow van der Waals well in the entrance channel.

P25 Diabatic Molecular Orbitals, Potential Energies, and Potential Energy Surface Couplings

by the Fourfold Way for Photodissociation of Phenol

Xuefei Xu, Ke R Yang, and Donald G. Truhlar*

Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of

Minnesota, Minneapolis, MN 55455-0431 USA

Complete-active-space self-consistent-field (CASSCF) calculations provide useful reference wave functions for configuration interaction or perturbation theory calculations of excited-state potential energy surfaces including dynamical electron correlation. However, the canonical molecular orbitals (MOs) of CASSCF calculations usually have mixed character in strong interaction regions; therefore, they are unsuitable for diabatization using the configurational uniformity approach. Here CASSCF diabatic MOs[1-3] for phenol have been obtained by the fourfold way, and comparison to the CASSCF canonical MOs shows that they are much smoother. Using these smooth CASSCF diabatic MOs, we performed direct diabatization calculations for the three low-lying states (Vtc, 1kk*, and 1^a*) and their diabatic (scalar) couplings at the dynamically correlated multi-configuration quasidegenerate perturbation theory (MC-QDPT) level. The present diabatization method is confirmed to be valid for the coupled O-H dissociation and C-C-O-H torsion, for vibrations along the v 16a and v 16b out-of­ plane ring modes, and for significantly distorted ring structures along reaction path connecting the planar equilibrium geometry of phenol to its strongly distorted prefulvenic form. The present work shows that diabatization at MC-QDPT level employing CASSCF diabatic MOs can be a good starting point for multi-dimensional dynamics calculations of photochemical reactions.

[1] H. Nakamura and D. G. Truhlar, J. Chem. Phys. 115, 10353 (2001). [2] H. Nakamura and D. G. Truhlar, J. Chem. Phys. 117, 5576 (2002). [3] K. R. Yang, X. Xu, and D. G. Truhlar, Chem. Phys. Lett. 573, 84 (2013).

P26 State-specific Rate Coefficients for H (vj) + H (v'j') Dissociation and Energy Transfer

Margot E. Mandy

Program in Chemistry, The University of Northern British Columbia,

Prince George, British Columbia, CANADA V2N 4Z9

mandy@unbc. ca

The calculation of state-specific cross sections and rate coefficients for collisional outcomes of H (vj) + HJv'j') presents challenges. Except in the case of a few low (v,j) states, full dimensional quantum calculations are intractable so alternative methods of calculation such as the quasiclassical trajectory method must be employed. For dissociation, the initial state of both molecules must be explicitly considered. In the case of energy transfer, both the initial state and the final state of both molecules must be taken into account, meaning that for a particular combination of initial states there are over 60000 possible outcomes to be considered. When exchange has occurred, ortho and para degeneracy must be properly weighted. Extensive quasiclassical trajectory calculations have been carried out on a chemically accurate potential energy surface to calculate the state-specific cross sections and rate coefficients for dissociation of H (vj) + H (v'j') for all combinations of (v, j) states with internal energy below 1 eV. This existing database of trajectory results is now being used to develop an efficient algorithm for the calculation of energy transfer cross sections and rate coefficients. Detailed balance is considered and systematic errors due to binning of trajectory results are assessed. Results are compared to quantum calculations where available. The resulting rate coefficients will be used in master equation studies of shocked H2gas.

P27 Merged-beam studies on neutral molecular beams Benjamin Bertsche, Andreas Osterwalder

Institute of Chemistry and Chemical Engineering, Ecole Polytechnique Federale de Lausanne, Switzerland

During the past 15 years many groups have invested in the optimization of the control of neutral molecular beams. One primary goal has been to produce molecules that are translationally and internally cold, and one of the main target applications are molecular collisions at temperatures in the 1 K-range and below. This temperature range to date has not been reached using crossed- beam techniques, even with decelerated beams. Nevertheless, there is tremendous interest in studying that range, both for the fundamental investigation of molecular scattering dynamics, and for quantitative laboratory-studies of interstellar chemistry.

To avoid the problems inherent to crossed-beams studies at low temperatures we are instead using merged neutral beams. This allows to work with the full density and low temperature provided by a supersonic expansion. By merging two beams we can reach relative velocities in the moving frame-of-reference corresponding to temperatures considerably below 1 K. While we do not have to decelerate beams, we still greatly benefit from the technological developments in the field of cold-molecules by using two guides to overlap the molecular beams. These guides, one being magnetic while the other one electric, at the same time control the direction of the beam and purge the molecular sample from all particles with unsuitable Stark- or Zeeman shift, and the resulting samples will be, to a very high degree, pure to a single rotational state of one particular species.

P28 UV Spectroscopic Characterization of an Alkyl Substituted Criegee Intermediate CH3CHoO

Joseph M. Beames, Fang Liu, Lu Lu and Marsha I. Lester Department of Chemistry, University of Pennsylvania Philadelphia, PA 19104-6323

Ozonolysis of alkenes in the troposphere proceeds through a Criegee intermediate, or carbonyl oxide, which has only recently been detected in the gas phase.1-4 The present study focuses on the production of an alkyl-substituted Criegee intermediate, CH3CHOO, in a pulsed supersonic expansion, and then utilizes VUV photoionization at 118 nm and UV-induced depletion of the m/z=60 signal to probe the B 1 A' ^ X 1 A' electronic transition. The UV-induced depletion approaches 100% near the peak of the profile at 320 nm, indicating rapid dissociation dynamics in the B state, and corresponds to a peak absorption cross section of ~5 x 10-17 cm12 3 molec-1. The UV absorption arises from a n*^n transition localized primarily on the carbonyl oxide group. The electronic spectrum for CH3CHOO is similar to that reported recently for CH2OO,2 but shifted 15 nm to shorter wavelength, which will result in a longer tropospheric lifetime for CH3CHOO with respect to solar photolysis. Nevertheless, the solar photolysis rates for the both of these small Criegee intermediates are comparable to those for their key bimolecular reactions under ambient conditions in the troposphere.1,4 Complementary electronic structure calculations (EOM-CCSD) are carried out for the B and Xpotentials of these Criegee intermediates along the O-O coordinate. An intramolecular interaction stabilizes the ground state of the syn-conformer of CH3CHOO relative to anti-CH3CHOO, and indicates that the syn- conformer will be the more abundant species in the expansion, as also found in a recent photoionization study. 4 The excited B electronic state of syn-CH3CHOO is also predicted to be destabilized relative to that for anti-CH3CHOO and CH2OO, in accord with the shift in the B-X transition observed experimentally. Hydroxyl radicals produced from thermal decomposition of energized Criegee intermediates are detected by 1+1' resonance enhanced multiphoton ionization and laser-induced fluorescence. The OH yield observed from CH3CHOO is 4-fold larger than that from CH2OO, consistent with prior studies of OH generation from alkene ozonolysis.

1. O. Welz, J. D. Savee, D. L. Osborn, S. S. Vasu, C. J. Percival, D. E. Shallcross, and C. A. Taatjes, Science 335, 204 (2012). 2. J. M. Beames, F. Liu, L. Lu, and M. I. Lester, J. Am. Chem. Soc. 134, 20045 (2012). 3. Y.-T. Su, Y.-H. Huang, H. A. Witek, and Y.-P. Lee, Science 340, 174 (2013). 4. C. A. Taatjes, O. Welz, A. J. Eskola, J. D. Savee, A. M. Scheer, D. E. Shallcross, B. Rotavera, E. P. F. Lee, J. M. Dyke, D. K. W. Mok, D. L. Osborn, and C. J. Percival, Science 340, 177 (2013).

P29 Extending Diffusion Monte Carlo to the Simultaneous Calculation of Multiple Rotationally Excited States of Highly Fluxional Molecular Systems

Andrew S. Petit, Jason E. Ford, and Anne B. McCoy

Department of Chemistry and Biochemistry The Ohio State University, Columbus, OH 43210

High resolution, rotationally resolved spectroscopy is among the most powerful tools for probing molecular structure and dynamics. Likewise, rotational spectroscopy provides the key technique for identifying the molecules and studying the chemistry present in the interstellar medium. While predicting and interpreting the spectral patterns of relatively rigid molecules has become straightforward, systems that exhibit large-amplitude, zero-point vibrational motions often present pathologically complicated spectra that can be very challenging to understand. Diffusion Monte Carlo (DMC) has widely been shown to be a powerful theoretical approach for calculating the energies and properties of the ro-vibrational states of highly fluxional molecules and clusters.

Here, we report the development of a DMC methodology capable of simultaneously describing multiple rotationally excited states of systems with pronounced rotation-vibration coupling and large-amplitude, zero-point vibrational motions within a single calculation. As in standard DMC, the wave function is represented by an ensemble of 5-functions, or walkers, that diffuse throughout configuration space. However, in this approach, each walker is dressed by a set of 2J+1 rotational state vectors. Each of these rotational state vectors evolves under the action of the rigid-rotor asymmetric top Hamiltonian constructed from the inverse moment of inertia tensor evaluated in the Eckart frame at the walker’s instantaneous position in configuration space. We have explored different approaches for determining the rotational energies of each of these rotational state vectors including the direct evaluation of the expectation value of the instantaneous rotational Hamiltonian as well as localization onto specific rigid-rotor basis functions through a surface hopping based procedure.6 We will demonstrate the validity of this approach through calculations performed on H2D+ and H3O+. We will also present preliminary results of our calculations of the pure rotationally excited states of CH5+ and its isotopologues. Finally, the insights that can be obtained from these calculations into the nature and strength of the vibration-rotation coupling present in these highly fluxional molecules will be briefly discussed.

a A.B. McCoy, Chem. Phys. Lett. 321, 71 (2000).

P30 The Singlet and Triplet PES of C4, and the anharmonic vibration analysis of singlet cyclic C4 and Xiaohong Wang and Joel M. Bowman Department of Chemistry, Emory University, Emerson 516L Atlanta, GA 30322 We report both singlet and triplet potential energy surfaces (PESs) for C4. The two PESs describe the rearrangement from linear to cyclic C4 isomers. The triplet PES and most configurations in the singlet PES are based on the CCSD(T)/cc-pVDZ ab. initio calculations, with a few thousands CASPT2(16,12)/cc-pVDZ points covering multireference regions on the singlet PES. The ab. initio calculations of C4 are very sensitive to the methods and basis, and experiencing multi-reference properties. This is the first time that the PESs of C4 are reported. The lowest intersystem crossing point for the triplet and singlet PES is located, and the large spin-orbit coupling constant indicates the fast crossing between the two electronic states may occur. In addition, the ground singlet cyclic C4 shows great anharmonicity. To carry out the vibrational anaylsis of cyclic C4 accurately, a more local PES around the singlet C4 cyclic minimum is constructed using CCSD(T)-F12b/aug-cc-pVTZ. The Multimode calculations are carried out using the PES, from which we obtain the accurate spectroscopic parameters of the singlet cyclic C4.

Financial support from NASA is gratefully acknowledged.

P31 Vibrational Analysis of an Ice Ih Model from 0-4000 cm"1 using the Ab Initio WHBB

Potential Energy Surface

Hanchao Liu, Yimin Wang and Joel M. Bowman

Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory

University, Atlanta, Georgia 30322

We present an analysis of the vibrational modes of a model of hexagonal ice, ice Ih,

comprised of 192 monomers with a core region of 105 monomers, using the ab initio WHBB

potential energy surface [Wang, Y.; Shepler, B.; Braams, B. and Bowman, J. M. J. Chem. Phys.

2011, 134, 094509.] A standard normal-mode analysis and a local-monomer normal-mode

analysis of 105 core monomers are performed to obtain harmonic frequencies and state densities

of the “pseudo-translation” (0-400 cm-1) , and “libration” (500-1100 cm-1) and monomer bend

fundamental (~1600 cm) and O-H stretch (~3000-3700 cm-1) bands. In addition, the coupled

local-monomer model is used to obtain the vibrational density of states in the bend fundamental

and O-H stretch regions. The harmonic and local-monomer vibrational density of states obtained

from core monomers are in good agreement with inelastic neutron scattering spectra. Full and

partial deuteration is also considered and the vibrational density of states is again compared to

experiment, where good agreement is found. We gratefully acknowledge financial support from

National Science Foundation (CHE-1145227).

P32 Anharmonic Vibrational Properties from Intrinsic n-Mode State Densities

Eugene Kamarchik and Ahren W. Jasper

Combustion Research Facility, Sandia National Laboratories, California 94551, USA

We present a method for calculating fully anharmonic vibrational state densities, state counts, and partition functions which makes use of the intrinsic density of states, that is, the states arising from a particular vibrational mode, mode pairing, or higher-order mode coupling. By using only low-order intrinsic densities the fully-coupled anharmonic vibrational result can be constructed, recovering a large fraction of the total anharmonicity and a significantly reduced computational cost. We demonstrate the method by its application to the classical phase space integrals for the densities of states in methane, CH4, and cyclopropene, C3H4.

Full-dunensional MC — 2-dimensional MC 1 -dimensional MC

10000 12000 14000 Energy (cm" )

Comparison of separable (1-dimensional) and pairwise coupled (2-dimensional) densities of states for C3H4

with the full-dimension result.

P33 Product-State-Resolved Dynamics of the Elementary Reaction of Atomic Oxygen with Molecular Hydrogen, O(3P) + D2 ^ OD(X2n) + D.

Sridhar A. Lahankar 1 , Jianming Zhang 1 , Kenneth G. Mckendrick2 * , Timothy K. Minton 1 * . department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. 2School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH-14 4AS, UK. Elementary three-atom systems provide stringent tests of the accuracy of ab initio theory. One such important reaction, O(3P) + H2 ^ OH(X2n) + H, has eluded detailed experimental study because of its high activation barrier. In this reaction, both the ground-state reactant atom and product diatomic molecule have open-shell character, which introduces the intriguing complication of non-Born-Oppenheimer effects in both the entrance and the exit channels. These effects may be probed experimentally in both the fine-structure and the A-doublet splittings of the OH product. We have used laser-induced fluorescence to measure OD internal product-state distributions from the analogous reaction of O(3P) with D2, enabled by a unique high-energy O(3P) source. We find that the OD (v' = 0) product is rotationally highly excited, in excellent agreement with earlier theoretical predictions. However, the distributions over the OD(X2n) fine-structure and A-doublet states, diagnostic of electronic non-adiabaticity in the reaction, challenge the prevailing theoretical understanding.

Nature Chemistry 5, 315-319 (2013)

P34 Calculations of Coupled Anharmonic Vibrational Frequencies from Local Monomer and Huckel Type Approximations: Application to (HCl)i-6

John S. Mancini and Joel M. Bowman

Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322

Presented is a method for determining anharmonic frequencies for molecular clusters and an application to hydrogen chloride clusters. Our method is founded on a localized approach to molecular vibrations whereby each monomer is treated separately in the cluster, greatly reducing the total number of degrees of freedom to be considered. Due to the cyclic and highly symmetric nature of the HCl clusters, degeneracies in local frequencies occur. Coupling of the modes via a simple Huckel approximation allows for these degeneracies to be lifted. The resulting frequencies all show substantially better agreement with experiments than their harmonic counterparts.

Financial support from the National Science Foundation is gratefully acknowledged

P35 Computational framework for studying H-bonding in the OH stretch region LauraC. Dzugan and Anne B. McCoy Department of Chemistry and Biochemistry The Ohio State University In many H-bonded complexes, there are two types of bands in the OH stretch region of the vibrational spectra; narrow peaks due to isolated OH stretches and a broadened feature reflecting the OH stretches involved in strong hydrogen bonding. This second region can be as wide as several hundred wavenumbers and is shifted to the red of the narrow peaks. In this work we focus on (CaOH)+-(H2O)n systems,1 and when n=4, the hydrogen bonding feature is several hundred wavenumbers wide. This is indicative of coupling between the OH stretches of the water molecules to the low frequency modes of the complex. To understand the broadening observed in the spectra, we have developed a computational framework in which we sample a Gaussian distribution of normal mode displacement geometries from equilibrium. Then we convolute the harmonic spectra of the OH stretches for each geometry into one spectrum. The frequencies and intensities of the normal modes are calculated by both Cartesian and internal coordinates to provide a complete analysis. 1. Leavitt, C.M.; Johnson, C.J.; Johnson, M. A. Unpublished work.

P36 UV-Photoelectron Spectroscopy of o-, m-, and ^-Methylphenoxide Anions Wilson K. Gichuhi, Elisa Miller, Dan Nelson, Veronica M. Bierbaum and W. Carl Lineberger JILA and Department of Chemistry and Biochemistry, University of Colorado, 440 UCB, Boulder, Colorado 80309, United States Abstract We report the 364 nm ultraviolet photoelectron spectra of o-, m- and p-methyphenoxide anions. The electron affinities (EAs) of the o-, m-, and p- methylphenoxyl radicals are found to be 2.197(7), 2.224(7) and 2.123(6) eV, respectively. The photoelectron spectra of the three anions are successifully reproduced by a Franck-Condon (FC) simulation based on the optimized geometries and the normal vibrational modes obtained from DFT electronic structure calculations at the B3LYP/6-311++G(2d,2p) level. In the the o-methylphenoxide spectrum, we observe two vibrational frequencies of 456 ± 30 and 556 ± 30 cm-1. These two frequencies represent ring distortion modes of the o-methylphenoxyl radical in its electronic ground state. The m-methylphenoxide spectrum exhibits an in-plane ring distortion vibrational progression with an observed fundamental frequency of 516 ± 30 cm-1. Two vibrational frequencies of 452 ± 20 cm-1 and 800 ± 60 cm-1 are observed in thep-methylphenoxide spectrum. The 452 ± 20 cm-1 is a CCC in-plane ring-distortion mode while the 800 ± 60 cm-1 is a ring-breathing mode of the p-methylphenoxyl radical in its electronic ground state. For each of the o-, m- and p- methylphenoxide PE spectra, we observe a hot band that correspond to population of v= 1 in the ring distortion vibrational mode of the anion. The values (in cm-1) for these vibrations are 540 ± 100, 516 ± 50 and 450 ± 50 for the o-, m- and p-methylphenoxide anions, repectively. Using the measured EAs together with the known O-H bond dissociation energies of the o-, m- and p- methylphenols ((D0 (CH3PhO-H)), a negative ion thermochemical cycle is utilized to obtain the deprotonation enthalphy(Aacid H0 (CH3PhO-H)) of the three methyl - substituted phenol isomers, commonly known as cresols . The values for the Aacid H0 for the o-, m- and p-cresol are determined to be (in kcal/mol) 347.36 ± 0.2, 347.63 ± 0.2 and 348.46 ± 0.2, respectively. Supported by NSF Grants CHE-1213862 (WCL) and CHE-1012321 (VMB) and AFOSR (WCL and VMB) Grant FA9550-12-0125

P37 Full-dimensional ab initio potential energy surface of

formaldehyde and trans-lcis- hydroxycarbene and 6d quantum

vibrational calculations of the isomerization of three species

Yimin Wang and Joel M. Bowman

Cherry L. Emerson Center for Scientific Computation and Department of Chemistry,

Emory University, Atlanta, GA 30322

We report a new full-dimensional semi-global potential energy surface (PES) of H2

CO that spans formaldehyde and hydroxycarbene isomers and barriers separating them. A total of 31 986 electronic energies were obtained using UCCSD(T)-F12/aug-cc-pVTZ. The root-mean-square fitting error is about 34 cm-1 for energies up to 22 000 cm-1 above the global minimum. We describe the exact 6 d quantum calculation that solves vibrational eigenstates of formaldehyde, trans- and cis-HOCH all at once.

P38 Structure and Thermochemistry of Dehydrocresols

Daniel J. Nelson, Wilson Gichuhi, Veronica M. Bierbaum, and W. Carl Lineberger Department of Chemistry and JILA University of Colorado, Boulder

A variety of dehydro o-, m-, andp-cresol diradicals have been investigated using photoelectron spectroscopy of the corresponding anions. The anions were generated via O- abstraction of H2+ from the cresol reactant in a flowing afterglow - photoelectron spectrometer apparatus. Using calculated energies and geometries for the most likely isomeric forms of the radical anions, simulated anion photoelectron spectra were obtained. The photoelectron spectra allow direct measurement of the electron affinity, and comparison of the simulated spectrum with the observed vibrational progressions in the spectra enabled the determination of the cresol sites involved in the loss of H2+. While the current results are preliminary, it appears that in every case the H2+ abstraction constituents come from the hydroxyl and methyl sites on cresol. Other possibilities that were considered include H2+ abstraction entirely from the methyl group, from the methyl group and the ring, and from the hydroxyl group and the ring. Gas phase acidities and bond strengths of these diradicals will be determined through acidity bracketing measurements using tandem flowing afterglow-selected ion tube (FASIFT) mass spectrometry.

Supported by NSF Grants CHE1213862 (WCL) and CHE1012321 (VMB) and AFOSR (WCL and VMB) Grant FA9550120125.

P39 A Gaussian Binning (1GB) analysis of vibrational state distributions in highly excited H2O from reactive quenching of OH* by H2

Riccardo Conte,1 Bina Fu,2 Eugene Kamarchik, 3 and Joel M. Bowman1 ^Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA. 2) State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China. 3) Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 USA.

As shown in experiments by Lester and coworkers [D. T. Anderson, M. W. Todd, and M. I. Lester, J. Chem. Phys. 110, 11117 (1999)], the reactive quenching of OH* by H2 produces highly excited H2O. Previous limited analysis of quasiclassical trajectory calculations using standard Histogram Binning (HB) was reported [B. Fu, E. Kamarchik and J. M. Bowman, J. Chem. Phys 133, 164306 (2010)]. Here we examine the quantized internal state distributions of H2O in more detail, using two versions of Gaussian Binning (denoted 1GB). In one version standard harmonic energies are used in the analysis (1GB-H) and in a novel version accurate quantum vibrational energies are employed (1GB-EQ). Data from 42,000 trajectories from our previous calculations that give excited water molecules are used in the two versions of 1GB as well as HB. The purely classical internal energy distribution serves as a benchmark at high energies, where the density of quantum states is high and quantum and classical distributions are expected to be similar. The 1GB discretization methods reconstruct the classical distribution better than HB. Some significant differences are found for the bending excitation probabilities between the 1GB approaches and for the O-H stretch excitation between 1GB and HB. Finally, we investigate deeper inside the asymmetric stretch distributions, since it is the mode with the biggest change in dipole momentum, giving the most intense experimental signal.

Financial support from the Department of Energy is gratefully acknowledged.

P40 Dyson orbitals within EOM-CCSD formalism

Anastasia O. Gunina, Anna I. Krylov

University of Southern California, Los Angeles, CA

Dyson orbitals are the objects representing an overlap between initial N-electron and

final N-1 electron wavefunctions for the ionization process. They can be used for modeling

of such experiments as orbital imaging, Compton profiles and electron momentum spectra.

Photoelectron matrix elements, which characterize probability to find system in specific final

state for a given initial state, can be written using Dyson orbitals as well, and these matrix

elements are used for calculation of many spectroscopically important quantities, including

total and differential ionization cross-sections.

Dyson orbitals can be computed for any initial and final many-electron wavefunctions,

however, CCSD/EOM-CCSD formalism provides a straightforward way of their evaluation

as well as including correlation and orbital relaxation effects. Currently, there exists an

implementation in a form of rows or columns of the EOM-EE-CCSD transition density

matrix [1], where EOM-EE-CCSD method is modified by adding very diffuse orbital for

simulating ionization process via excitations to this diffuse orbital. In this work, proper

EOM-IP/EA-CCSD implementation is presented. Both ground and excited initial states cases

are discussed. The orbitals are computed for several test cases and applied for calculating

ionization cross-sections.

1. C.M. Oana, A.I. Krylov, J. Chem. Phys. 127, 234106 (2007)

P41 Disagreement Between Theory and Experiment for High Rotationally Excited Products of

H+D2 => HD(v’, j’) + D Reaction

Justinas Jankunas1, Mahima Sneha1, Richard N. Zare1, Foudhil Boukaline2, Stuart C. Althorpe 3

1 Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA

2Max Born Institute, Max Born Strasse 2a, 12489 Berlin, Germany

3 Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2IEW, United Kingdom

The H+H2 reaction and its isotopic variants has been one of the most studied reactions in the field of gas phase reaction dynamics both experimentally and theoretically. It is only reasonable to expect that at this point theory and experiment would have a nearly perfect agreement. Our recent findings 1 however, say otherwise. We have recently measured state resolved differential cross sections (DCSs) of the HD product of the H+D2 reaction over a wide range of collision energies and internal states using the photoloc technique. The experimental results were compared with fully dimensional time independent QM calculations on the refined BKMP2 potential energy surface. While most of the HD (v', j') product states with low to medium rotational excitation show a nearly quantitative agreement between theory and experiment, the agreement worsens as the rotational angular momentum of the HD product increases (Figure 1). This disagreement is not limited to vibrationless HD products, but is found in several other HD(v', j') vibrational manifolds. The reason behind this discrepancy could be either inaccuracy in the PES, an experimental artifact, or a combination of both. The puzzle remains to be solved.

9, degrees 9, degrees

Figure 1: DCS for HD(v', j') products of the H + D2 ^ HD(v', j') + D reaction. Circles are the experimental data, error bars correspond to one standard deviation of three to five independent measurements. Red circles are a fit of an experimental data to theory wherein the peak heights are matched. Black curve is the blurred TD-QM calculations. 1. J. Jankunas, M. Sneha, R. N. Zare, F. Boukaline, and S. Althorpe, J. Chem. Phys. 138, 094310 (2013) and references therein.

P42 Ion-Neutral Chemistry in the Sub-Kelvin Regime

Felix H. J. Hall1, Pascal Eberle1, Gregor Hegi 1, Maurice Raoult12 , 3Mireille 4 Aymar2, Nadia Bouloufa-Maafa2, Olivier Dulieu2 and Stefan Willitsch1

department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland 2Laboratoire Aime Cotton du CNRS, 91405 Orsay Cedex, France

We present the results of combined experimental and theoretical investigations into cold reactive collisions between laser- or sympathetically cooled ions and Rb atoms in an ion-atom hybrid trap. We compare the collision systems of Ca+ + Rb [1,2] and Ba+ + Rb [3], in which both species are laser cooled, and find that for both systems the rate of reaction is considerably enhanced in electronically excited channels. These observations are rationalised with reference to computed potential energy curves calculated using high level electronic structure methods. We find that radiative processes play an important role in both systems, verified by the observation of the radative association products CaRb+ and BaRb+ and rationalised using quantum scattering calculations.

We also compare these results on atomic ion systems with collisions of

sympathetically cooled N2+ molecular ions in their vibrational ground state with ultracold Rb

atoms with average collision energies (/kB) down to 20 mK [4]. To our knowledge, this is the first time that reactive collisions with molecular ions have been studied at mK energies. We find that the reaction rate is a factor of ~4 faster than the Langevin rate from the Rb (5p) state, and is two orders of magnitude faster than in the atomic Ca+ + Rb system. The fast rate is explained by a near resonance between entrance and product channels at short range, and the strong charge-quadrupole interaction in the Rb (5p) + N2+ entrance channel at long range. A classical capture model including these effects reproduces the observed rate.

[1] Felix H.J. Hall et al; Phys. Rev. Lett. 107, 243202 (2011) [2] Felix H.J. Hall et al; accepted by Mol. Phys. (D0I:10.1080/00268976.2013.780107; arXiv:1302.4682) [3] Felix H.J. Hall et al; accepted by Mol. Phys. (D0I:10.1080/00268976.2013.770930; arXiv:1301.0724) [4] Felix H.J. Hall et al; Phys. Rev. Lett. 109, 233202 (2012)

P43 Solvent Dependent Dynamics of Salicyidene Aniline in Supercritical CO2 Ryan Kieda, Adam Dunkelberger, and F. Fleming Crim Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706

Salicylidene aniline has been studied extensively as a prototype excited state intramolecular proton transfer (ESIPT) system and shown to exhibit changes in its photoisomerization dynamics depending upon the solvent environment it experiences. We present work developing an apparatus to conduct ultrafast transient absorption experiments using supercritical C02 as a solvent with the capability to vary density through temperature and pressure, as well as co-solvent percentage. We have used this system to investigate the photoisomerization dynamics of salicylidene aniline in mixed solutions of 1-propanol and supercritical C02. The rate at which the transient absorption signals decay varies with the percentage of 1-propanol in the solution and appears to scale linearly with the bulk solvent solution viscosity. The wavelength dependent nature of this viscosity relationship provides insight into the reaction mechanism.

P44 Molecular quantum gyroscopes in an optical centrifuge

Carlos Toro, Qingnan Liu, Matthew J. Murray, Amy S. Mullin

Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742

The control of direction and magnitude of the angular momentum of molecules offers a stimulating subject for exploring directionality in chemistry and physics. Creating highly rotationally excited molecules, known as super rotors , represents a unique opportunity to study extremely oriented angular momentum systems with interesting and exceptional collisional properties. The optical centrifuge allows one to trap molecules in a strong optical field and spins them to high rotational states due to the angular acceleration of the optical field. Here, we report collisionally-induced quantum state-specific dynamics of molecules in an optical centrifuge by performing polarization dependent, high resolution transient IR absorption measurements for a number of C02 rotational states. These results demonstrate that the initial angular momentum orientation is long-lived and persists even after thousands of collisions, indicating that molecules in an optical centrifuge behave as quantum gyroscopes. These observations demonstrate that the optical centrifuge prepares an anisotropic rotational distribution and that molecules in oriented, ultra-high angular momentum states require many more collisions to randomize their orientation than do those in low rotational states.

P45 Study of Photodissociation of Phenol with Combined Quantum Mechanics/ Molecular

Mechanics Potential Energy Surfaces by Fourfold Way Diabatization

Ke. R. Yang, Xuefei Xu, and Donald G. Truhlar*

Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431 USA

The theoretical treatment of nonadiabatic processes involving more than one potential

energy surface (PES) can be carried out in either an adiabatic or a diabatic representation.

With the diabatic representation, one can eliminate the use of rapidly changing and singular

vector couplings; but the diabatic states are not uniquely defined and depend on the chosen

diabatization scheme. Fourfold way diabatization is a general method to obtain diabatic

states.[1] A new algorithm has been proposed to obtain diabatic states and their scalar

couplings at the multi-configuration quasi-degenerate perturbation theory (MC-QDPT) level with complete-active-space self-consistent-field (CASSCF) diabatic molecular orbitals

(DMOs).[2] Diabatic potentials and their couplings are smooth enough to be fitted by

analytic representations for dynamical studies, and here we do that for phenol, where we treat the O-H dissociation coordinate and the C-C-O-H torsion mode quantum mechanically and

the other modes molecular mechanically by a generalization of the combined valence bond-

molecular mechanics (CVBMM) method.[3] The PESs of the three low-lying states and their

scalar couplings are fitted with analytical functions and will be used for full-dimensional

quasiclassical dynamic studies.

[1] H. Nakamura and D. G. Truhlar, J. Chem. Phys. 115, 10353 (2001). [2] K. R. Yang, X. Xu, and D. G. Truhlar, Chem. Phys. Lett. 573, 84 (2013). [3] A. Chakraborty, Y. Zhao, H. Lin, and D. G. Truhlar, J. Chem. Phys. 124, 044315 (2006).

* [email protected]

P46 Photodissociation Dynamics of Nitromethane and Methyl Nitrite by IRMPD Imaging

Arghya Dey,a Ravin Fernando,a Chamara Abeysekera,a Zahra Homayoon ,b JoelM. Bowman'.b

and Arthur G. Suits1a

a1Department of Chemistry, Wayne State University, Detroit, MI 48202

b:Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory

University, Atlanta, GA 30322

Photodissociation of nitroalkanes can occur via two major pathways; the first being the direct fission of the C-N bond to give NO2, while the second involves first isomerization to the nitrite, followed by dissociation into products. Earlier theoretical studies consistently found an isomerization barrier implausibly high to account for the isomerization channel. However, recent theoretical studies identified a loose transition state that involves “roaming-mediated ”

isomerization (RMI) involves near-dissociation to the NO2 channel, followed by recombination

as the nitrite then loss of NO.2 State resolved high-resolution imaging of the NO product was carried out to characterize this RMI in nitromethane. Using infrared multiphoton dissociation (IRMPD), one can dissociate the molecule at the dissociation threshold on the ground electronic state, leading to better understanding of the reaction mechanism, in particular for reactions involving roaming dynamics. IRMPD has long been used with photofragment translational spectroscopy, but imaging methods have become the technique of choice for many photochemistry studies. This work represents the first to combine IRMPD with imaging. The IRMPD images for the NO product show low translational energy release upon photodissociation. These findings are consistent with the earlier IRMPD studies which suggested the importance of

an isomerization pathway.3 Theoretical calculations carried out by Bowman and co-workers are also in good agreement with the experimental observations. IRMPD studies of methyl nitrite were also carried out for comparison where the dominant dissociation pathway is fission of O-N bond resulting in formation of CH3O and NO.

2 Zhu, R. S.: Lin, M. C. Chem. Phys. Lett. 2009, 478, 11. 3 Wodtke, A. M, Hintsa, E. J.; Lee, Y. T. J. Phys. Chem. 1986, 90, 3549. P47 Velocity Mapping Vibrationally Excited HCl from Bimolecular Reactions of Cl and

Alkenes

Thomas J. Preston, Greg T. Dunning, and Andrew J. Orr-Ewing

School of Chemistry, University of Bristol, Bristol, United Kingdom

Velocity-mapped ion-imaging coupled with resonance-enhanced multiphoton

ionization detects both the velocity and quantum state of gas-phase species. In a dual

molecular-beam ion-imaging apparatus, we explore the bimolecular reaction dynamics of

photolytically generated Cl with either propene or 2,3-dimethylbut-2-ene. Both of these

reactions are exothermic by at least 60 kJ/mol and produce vibrationally excited HCl

products. The HCl molecules born from the propene reaction are strongly forward scattered, vibrationally excited, rotationally cold, and have velocities that approach the thermodynamic

limit, all of which point to a stripping-type mechanism. The HCl molecules formed by

reaction with dimethylbutene are also vibrationally excited and rotationally cold, but their

velocities extend over a broader range of speeds and scattering angles than in the propene

reaction. The images show that hydrogen abstraction from dimethylbutene deposits energy

into both the HCl and polyatomic fragment, illustrating that the reaction proceeds by a route

that is more complicated than a direct stripping mechanism.

P48 Towards Spin-Orbit Coupled Diabatic Potential Energy Surfaces for Methyl Iodide Using Effective Relativistic Coupling by Asymptotic Representation

Nils Wittenbrink, Hameth Ndome, and Wolfgang Eisfeld Fakultat fur Chemie, Universitat Bielefeld, Bielefeld, Germany

The theoretical treatment of state-state interactions and the development of coupled multidimensional potential energy surfaces (PESs) is of fundamental importance for the theoretical investigation of nonadiabatic processes. Usually, only derivative or vibronic coupling is considered but the presence of heavy atoms in a system can render spin-orbit (SO) coupling important as well. Therefore, we have been developing a new method that allows to compute the SO effects very efficiently and provides a fully coupled diabatic potential energy model.1;2 The method is based on the diabatic asymptotic representation of the molecular fine structure states and an effective relativistic coupling operator. It therefore is called Effective Relativistic Coupling by Asymptotic Representation (ERCAR). In contrast to commonly used simpler approaches, the ERCAR method correctly accounts for the geometry dependence of the SO effects and thus is valid not only in the asymptotic region but also in the strong interaction region. It also is capable to handle allowed and avoided state crossings of all kinds. After testing this approach with a simple diatomic system, we now apply this methodology to generate SO coupled diabatic PESs along the C-I dissociation coordinate for methyl iodide (CH3I). This is the first and mandatory step towards the development of fully coupled full-dimensional PESs to describe the multi-state photodynamics of this benchmark system. This approach allows the efficient and accurate generation of fully coupled PESs including derivative and SO coupling based on high-level ab initio calculations. In the present study we present a specific ERCAR model for CH3I that so far accounts only for the C-I bond cleavage. Further coordinates will be included into the model step by step. Details of the diabatization are given and the accuracy of the results is demonstrated in comparison to reference ab initio calculations and experiments. The energies of the adiabatic fine structure states are reproduced in excellent agreement with ab initio SO-CI data. The model is also compared to available literature data and its performance is evaluated critically. This shows that the new method is very promising for the construction of fully coupled full-dimensional PESs for CH3I to be used in future quantum dynamics studies. 1

1. H. Ndome, R. Welsch, and W. Eisfeld, J. Chem. Phys., 136, 034103 (2012). 2. H. Ndome and W. Eisfeld, J. Chem. Phys., 137, 064101 (2012).

P49 Contrasting dynamics of reactive scattering at saturated and unsaturated liquid

hydrocarbon surfaces

Maria A. Tesa-Serrate, Kerry L. King, Grant Paterson, Robin E. Westacott, Matthew L. Costen

and Kenneth G. McKendrick

Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, U. K.

The dynamics of collisions of O(3P) and OH with the surfaces of the long-chain hydrocarbon liquids squalane (C30H62 , 2,6,10,15,19,23-hexamethyltetracosane) and squalene

(C30H50 , trans-2,6,10,15,19,23 -hexamethyltetracosa-2,6,10,14,18,22-hexaene) have been studied experimentally. The nascent OH products of reactive (for O(3P)) or inelastic (for OH itself) scattering from the surface were detected by LIF. Molecular dynamics simulations of the structure of the liquid surfaces support the interpretation of the experiments.

The inelastic scattering of OH from both liquids can be categorized empirically as a combination of limiting impulsive scattering (IS) and thermal desorption (TD) mechanisms.

There is enhanced reactive uptake of OH on the unsaturated squalene surface which we interpret, through the reduction in the TD component, as being an addition reaction at exposed double-bond sites.[1] Reactive scattering of O(3P) with squalene produces a lower yield of OH than from squalane, despite the substantial reduction in the C-H bondstrength of the allylic sites. We infer that O(3P) is also lost competitively at exposed unsaturated sites in squalene, but observe a clear signature of abstraction from allylic C-H sites in the enhanced rotational and vibrational excitation of the OH products.

[1] Kerry L. King, Grant Paterson, Giovanni E. Rossi, Marija Iljina, Robin Westacott,

Matthew L. Costen and Kenneth G. McKendrick, Phys. Chem. Chem. Phys., in press.

P50 Parity-Dependent Oscillations in the Transfer of Orientation in Inelastic Collisions of

CN(A2n) with Ar, N2, O2 and CO2

Stephen J. McGurk, Kenneth G. McKendrick and Matthew L. Costen

Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, U. K.

We present measurements of the propensity to conserve orientation in inelastic collisions of CN(A2n, v = 4) with Ar, N2, O2 and CO2. CN(X2E+) was prepared by photolysis of trace ICN in a bath of the collider gas, and allowed to translationally and rotationally relax.

Oriented samples of CN(A2n, v = 4) were then prepared in rotational fine-structure and parity-resolved levels (specifically j = 6.5 Fie, and j = 10.5 Ff) by circularly-polarized excitation on the A-X(4,0) band. The orientation of the prepared level, and that of product rotational levels populated by single collisions with the bath gas, was measured using

Frequency Modulated spectroscopy on the A-X(4,2) band.

The degree of orientation transferred in the collision is quantified by the multipole transfer efficiency, E (1)(j, j'), which ranges from +1 (total conservation) to -1 (complete change of sign of the orientation). For all four collision partners, we see striking oscillations of

E(1)(j, j') , as a function of the j'F's'. Collisions that conserve total rotational parity preferentially conserve orientation, whilst parity-changing collisions are found to result in significant loss, or even reversal in the sign, of the orientation. Quantum scattering calculations quantitatively reproduce the observed E(1)(j, j') for Ar .[1]

[1] S. J. McGurk, K.G. McKendrick, M. L. Costen, M. H. Alexander and P. J. Dagdigian, J.

Chem Phys. Submitted.

P51 Scattering-angle dependent product rotational alignment in inelastic collisions of electronically excited molecules: NO(A2£+)+Ne

J. D. Steill1, J. J Kay1, G. Paterson2, T. R. Sharples2, J. Kios 3 , M. L. Costen2, K. E. Strecker1,

K. G. McKendrick2, M. H. Alexander3 andD. W. Chandler1

1Sandia National Laboratories, Livermore, CA 94550, USA

2Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK

3 Department of Chemistry and Biochemistry, University of Maryland, MD 20742, USA

We report the first measurements of the scattering-angle resolved rotational polarization of the products of collisions of electronically excited molecules, together with

supporting quantum scattering (QS) calculations.1 A combination

of optical pumping and crossed-molecular beams was used to

prepare and collide NO(A2Z+, v = 0, N = 0) with Ne. The NO(A,

v = 0, N) products were probed by (1+1') velocity-map ion­

imaging with both horizontal and vertical probe laser c polarizations. Strong scattering-angle dependent oscillations were observed in the product rotational alignment. These are e qualitatively reproduced by QS calculations on an ab-initio PES, Fig 1. Velocity-map images but are inconsistent with the kinematic apse conservation of NO(A, v = 0, N = 4, 5, 7 & 9) fOT tenanted and . observed in NO(X2n)+Rg collisions. We propose that this results vertical probe polarizations. from the extended range of the relatively shallow repulsive core of the NO(A)-Ne PES, in contrast to the rigid repulsive core observed for NO(X2n)+Rg.

1 J. D. Steill, J. J. Kay, G. Paterson et al., J. Phys. Chem. A. DOI 10.1021/jp402019s (2013).

P52 Theoretical Studies of Photodissociation Dynamics of BrCN

Bernice Opoku-Agyeman and Anne B. McCoy

Department of Chemistry and Biochemistry

The Ohio State University, Columbus, OH 43210.

We present the results of quantum dynamics studies of photodissociation of BrCN- following electronic excitation to states that dissociate to Br- + CN and Br* + CN-. The electronic structure of BrCN- was evaluated with MRCI-SO/aug-cc-pVTZ at a fixed CN distance of 1.18 A. The calculations were used to evaluate the two-dimensional potential surfaces for the ground and excited states as functions of the Br-CN(center of mass) distances (R) and angle between CN and R. Due to the energy difference of ~0.05 eV between the states that dissociates into Br- + CN and Br* + CN-, a non-adiabatic interaction similar to that observed in ICN-[1] is expected to play an important role in the dynamics of BrCN- photodissociation. In this study, a diabatic model for the two relevant excited states was develop ed . F or 9 less than 90° (closer to BrCN- geometry), the two surfaces cross and contain wells that are at least 0 .1eV deep . In contrast, 9 greater than 90°, the curves do not cross and only the lower energy diabatic potential contains a well. As a result of the crossing of the curves only for Br-CN(center of mass) bond angles of less than 90o, the energy distribution between rotation and translation can have a large influence on the branching ratios of the photoproducts. This is investigated by quantum dynamics studies of wave packets initially excited to these two states. Preliminary results for excitation of the ground rovibrational state onto these two states indicate that shapes of the excited state potential energy surfaces play significant roles in the distribution of the photofragments during the quantum dynamic calculations. 1

[1] A. B. McCoy, W. C. Lineberger, A. S. Case, J. P Martin (Unpublished Manuscript)

P53 Elucidating the Decomposition Mechanism of Energetic Materialswith Geminal Dinitro Functional Groups Using 2-Bromo-2-nitropropane Photodissociation

Ryan S. Booth1, Chow-Shing Lam1, Matthew D. Brynteson1, Lei Wang1 and Laurie J. Butler1

The James Franck Institute and Department of Chemistry, University of Chicago, Chicago, Illinois 60637, USA

These experiments photolytically generate two key intermediates in the decomposition mechanisms of energetic materials with nitro substituents, 2-nitropropene and 2-nitro- 2-propyl radicals. We use a combination of crossed laser-molecular beam scattering and velocity map imaging to study the photodissociation of 2 -bromo-2-nitropropane at 193 nm and the subsequent unimolecular dissociation of the intermediates above. Our results demonstrate that 2-bromo -2-nitropropane has four primary photodissociation pathways: C-Br bond fission yielding the 2-nitro- 2-propyl radical, HBr elimination yielding 2 -nitropropene, C-N bond fission yielding the 2-bromo-2-propyl radical, and HONO elimination yielding 2-bromopropene. The photofragments are formed with significant internal energy and undergo many secondary dissociation events, including the exothermic dissociation of 2-nitro- 2-propyl radicals to NO + acetone. Calculations at the G4//B3LYP/6-311 + +g(3df,2p) level show that the presence of a radical at a nitroalkyl center changes the mechanism for and substantially lowers the barrier to NO loss. This mechanism involves an intermediate with a three-center ring rather than the intermediate formed during the traditional nitro-nitrite isomerization. The observed dissociation pathways of the 2-nitro-2- propyl radical and 2 -nitropropene help elucidate the decomposition mechanism of larger energetic materials with geminal dinitro functional groups.

P54 Photodissociation of 1-Bromo-2-propanol and 2-Bromo-1-propanol: A study of the Radical Intermediates Produced upon the Addition of OH to Propene M. D. Brynteson, C. C. Womack, R. S. Booth, and L. J. Butler Department of Chemistry and the James Franck Institute, University of Chicago, Chicago, Illinois 60637 Abstract We investigate the photolytic production of two radical intermediates in the reaction of OH with propene, one from addition of the hydroxyl radical to the terminal carbon and the other from addition to the center carbon. In a collisionless environment, we photodissociate a mixture of 1 -bromo-2-propanol and 2-bromo-1-propanol at 193 nm to produce these radical intermediates. The data shows that the nascent radicals have a distribution of vibrational energies spanning the dissociation barriers to various product channels. Using a combination of velocity map imaging and photofragment translational spectroscopy, we detected various photoprocucts, including those from the following dissociation channels: OH + propene, methyl + acetaldehyde, and ethyl + formaldehyde. Using a velocity map imaging apparatus, we measure the speed distribution of the recoiling bromine atoms, yielding the distribution of kinetic energies imparted to the nascent radicals + Br. Resolving the velocity distribution of Br(2Pi/2) and Br(2P3/2) separately allows us to determine the total (vibrational + rotational) internal energy distribution in the nascent radicals. By modeling the amount of rotational energy imparted to the radicals upon dissociation of the halogenated precursors, we determine the vibrational energy distribution of the nascent radicals. With this model, we predict the percentage of radicals having vibrational energy above and below the lowest dissociation barrier, that to OH + propene. We present data supporting the validity of this model as well as well as the data on the different dissociation channels.

P55 Gas-liquid interactions: a new experimental approach using liquid microjets

Alan Sage 1'2, Andrew Orr-Ewing 2 and Stuart Greaves1

1Heriot-Watt University, UK 2University of Bristol, UK

A novel apparatus has been constructed to study collisions between gas phase molecules and volatile liquid surfaces. The experiment has a liquid microjet at its heart: a narrow (~10-30 pm diameter) liquid filament which presents a clean, constantly refreshed surface that enables evaporating molecules to escape freely into the vacuum without undergoing secondary, gas-phase collisions.

Proof of principle experiments are focusing on collisions of hyperthermal chlorine atoms with the surface of a squalane jet. Cl(2P3/2) radicals are produced close to the liquid surface by 355 nm photolysis of Cl2 gas in a molecular beam. These radicals are subsequently scattered by the liquid surface and, after traveling into a skimmed, differentially pumped detection chamber, scattered species are ionized by REMPI and detected using time of flight methods. The new technique has great versatility, with potential in early experiments to detect Cl from elastic and inelastic and HCl from reactive scattering events. Quantum state distributions of scattered species are resolvable using this apparatus, as well as product kinetic energies and residence times at the liquid surface.

P56 Dynamics of Cl + propane, butanes reactions revisited with crossed-beam DC slice imaging

Baptiste Joalland, Yuanyuan Shi, Nitin Patel, Richard Van Camp, Arthur G. Suits

Department of Chemistry, Wayne State University, Detroit, USA

We present velocity-flux contour maps and their derived double differential cross sections (DCSs) for H/D abstractions in selected Cl + alkane reactions measured by means of crossed beam scattering and universal DC slice imaging. The approach adopted in this study consists in combining detection of the hydrocarbon radical product by 157 nm single photon ionization with a new high-density radical source. Angular and reduced translational energy distributions for the set of studied unsaturated hydrocarbons, namely propane, its two selectively labeled isotopologues (CD3CH2CD3 and CH3CD2CH3), and butane isomers n-butane and isobutane for which none or only interpolated DCSs were measured in the past, show distinct differences that allow us to revisit the “reaction picture” of this rich and well studied class of reactions. Dynamics associated with secondary and tertiary abstractions are clearly isolated for the first time. Radical product energy disposal and H vs. D abstraction are highlighted.

Left: DC sliced raw image of reactive scattering and nominal Newton diagram for the reaction of chlorine with n-butane at a collision energy of 13 kcal.mol-1. Right: Corresponding reduced translational energy distributions for 10° steps of the angular distributions.

P57 Photochemical dynamics on on excited states in ethylene cation

Baptiste Joallandl, Toshifumi Mori 2, Todd J. Martinez2, Arthur G. Suits1

1Department of Chemistry, Wayne State University, Detroit, USA

2PULSE Institute and Department of Chemistry, Stanford University, Stanford, USA

Ethylene cation is the simplest radical n system: one electron populates a unique n orbital in its ground state electronic configuration. The three first excited states are the results of on excitations for which torsional motion influences the balance between the two main photodissociation channels, C2H3+ + H and C2H2+ + H2. The intimate origin of this "twisting" effect is however unknown. The torsional excitation could directly give rise to prompt dissociation events in the excited states or populate different regions on the ground state after non-radi ative relaxation. We present a combined electronic structure/photochemical dynamics study that aims at investigating on these questions. Two families - planar and twisted - of minimum energy conical i intersections are characterized. Ab initio multiple spawning dynamical calculations suggest that ultsafast dynamics in the excited states can lock up the system in hineered rotation motions on the ground state potential energy surface when the prior non- adiabatic events involve twisted conical intersection seams. Overall, this study raises questions on the dynamics of highly electronically frustrated radicals and the role of low-lying conical intersections in vibrational energy redistribution.

O 45 SB IS? -"HE) O 45 SO ISj 'ffi T T

; v x.'X

"TfqEb "TFee/Eb

Typical D1/D0 trajectories involving conical intersections at torsional angles r of 0° (left) and 90° (right). Spawning events are highlighted with plain disks. Trajectories on D1 are represented in blue (initial: dark blue, backspawned children: sky blue), trajectories on DO in black (initial) and grey (after backspawns to Dl).

P58 Theoretical Studies of Roaming Dynamics in the Unimolecular Dissociation of

CH3NO2 to CH3O + NO

Zahra Homayoon and Joel M Bowman

Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA

Characteristic signatures of roaming are seen in the translational energy distribution in the products CH3O + NO from the unimolecular dissociation of nitromethane. Calculations on a new global potential energy surface reveal the detailed roaming-isomerization dynamics in this process, and these are supported by the experimental observations. Calculations find a characteristic of roaming, namely production of vibrationally excited CH3O, which is consistent with experiment.

P59 A pulsed anion source for production of cold, solvated anions and its applications to Argon­

tagging, rational ion synthesis, and H2-tagging

Yu-Ju Lu, Allan M. Oliveira, and W. Carl Lineberger

JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder,

Colorado 80309, USA

We present the development and characteristics of an unconventional pulsed anion source suitable for production of cold, solvated anions. The pulsed anion sourceutilizes two pulsed expansions, one with an electrical discharge that is merged to the main expansion, to generate cold, solvated anions. The main expansion, neat Ar or H2/Ar gas mixture, picks up and collisionally cools the anions in a supersonic expansion. The anions are formed in a discharge source, which is oriented perpendicular to the main expansion. These cold anions are easily tagged with weakly bound solvents, such as Ar or H2, to reduce the internal energy of the anions. To investigate reactive intermediates using photoelectron spectroscopy of anions, we perform a well-controlled chemical reaction that occurs through sequential addition of neutral reactants to cold anions. Here, we demonstrate the performance of this arrangement with photoelectron spectra of OH-(Ar)n=0-3,7,12 and 18, HOCO-, CH3O-(H2)0-3 , and CH3 .

Supported by NSF Grants CHE-1213862 and AFOSR Grant FA9550-12-0125

P60 Fluorine Atom Reactions in Solution

Greg T. Dunning, Fawzi Abou-Chahine, Andrew J. Orr-Ewing

School of Chemistry, University of Bristol, Bristol, United Kingdom

Fluorine atom reactions have featured at the forefront of advances in reaction dynamics in the gas phase. In the current work, the dynamics of F-atom reactions in the liquid phase are investigated on a picosecond timescale to explore how the dynamics are influenced by a solvent.

Fluorine atoms are created through the photolysis of XeF2 and then subsequently undergo rapid reaction with the solvent, CD2Cl2 or CD3CN. Time-resolved UV visible spectra confirm the XeF2 photolysis is a prompt source of F atoms, and also show the presence of

XeF(X) formed vibrationally hot. Time-resolved infrared absorption spectroscopy is used to monitor the DF products on a picosecond timescale. Using these absorptions, transient vibrational populations differences are derived. Vibrational relaxation rates of DF found from the fits agree well with results from a picosecond IR-pump IR-probe experiments.

Combining these results in a kinetic model shows the F atoms react with a bimolecular rate constant rate of 1.6x1010 M-1s-1 in CD3CN and 6.6x10 9 M-1s-1. The nascent vibrational distribution of the DF is inverted, but undergoes rapid vibrational relaxation with a time constant of ^3.5 ps due to the effective coupling of energy to the solvent.

The DF vibrational excitation and inverted population distribution are similar to previously observed dynamics in the gas phase. However in contrast to gas phase results, the extent of vibrational excitation is reduced. This decrease in nascent vibrational excitation has also been seen in our solution phase reactions of CN radicals and Cl atoms.

P61 Molecular Dynamics Study of the Relaxation of OH (v, J) in Argon

at High Pressures and Temperatures

Rezvan Chitsazi and Donald L. Thompson

Department of Chemistry, University Of Missouri-Columbia, Columbia, MO 65211

We are interested in developing a better understanding of the effects of high pressure on the relaxation of molecules and radicals, particularly at pressures beyond what is currently achievable experimentally, and for conditions where bimolecular collisional relaxation and energization may no longer be valid. The effects of pressure are usually treated within a method such as master equation simulations with parameters either measured or computed for isolated collisions. This is generally accepted as valid for many conditions of interest, but it may not be at extreme pressures. We are using a direct approach in which we place an excited molecule or radical in a simulation box (equilibrated for NPT and NVT ensembles) with an inert bath gas to apply pressure, and then propagate the system forward in the NVE ensemble to determine the sequence of events and nature of the energy transfer. We have begun with studies of the important simple radical OH. We have performed simulations of the relaxation of highly excited

OH radicals in Ar up to pressures at which the bimolecular collision assumption breaks down.

The emphasis of the presentation will be on the relaxation mechanisms for OH (v, J) for internal energies up to the dissociation limit for pressure and temperature ranges that include and exceed those achievable in the laboratory.

P62 Improved Multidimensional Semiclassical Tunneling Theory

Albert F. Wagner

Chemical Sciences and Engineering Division, Argonne National Laboratory

A semiclassical, multidimensional, analytic tunneling expression developed by Miller et al.1 is often used for thermal kinetics (e.g., as in the MultiWell Program Suite). This expression is built off of second order vibrational perturbation theory at the saddle point and as such incorporates both the imaginary frequency and the anharmonicity and multi-mode coupling with the reaction coordinate represented by elements of the x matrix. While the expression is reliable for tunneling near the top of the barrier, it is unfortunately qualitatively incorrect for deep tunneling at energies decidedly below the barrier. This occurs because the expression does not know how far down from the top of the barrier the reactant and product asymptotes are. Instead it constructs a reactant asymptotic energy consistent with what it does know, namely the imaginary frequency and the x matrix elements. To correct this deficiency, there are two ways to incorporate barrier height information while retaining a semiclassical, multidimensional analytic expression. First one can determine an effective third-order coupling matrix that represents the effect of the barrier height from the reactant direction. Second one can modify the potential consistent with the expression to incorporate the barrier information from both the product and reactant directions. Since both approaches retain the harmonic frequency and x matrix element information, they correctly transform into the Miller expression at thermal energies near the top of the barrier. The poster will describe the analysis, present the final formulas, and provide illustrative results.

1. W. H. Miller, R. Hernandez, N. C. Handy, D. Jayatilaka, and A. Willets, Chem. Phys. Letts.

172, 62 (1990).

P63 Diffusion Monte Carlo Calculations of H7+ and its isotopomers

Chen Qu and Joel M. Bowman

Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory

University, Atlanta, GA 30322

Diffusion Monte Carlo (DMC) calculations were performed for H7+ and all its

possible deuterated isotopologues and isotopomers using the recent analytical potential

energy surface (PES)[1]. The dissociation energy D0 of 752±15 and 980±14 cm-1 for H7+ and

D7+ are determined for the first time. The wavefunction indicates that the vibrational ground

state H7+ can be described as two rotating H2 bounded to a relatively localized H3+ core.

DMC calculations for the deuterated isotopomers predict that the preferred arrangement is

the one that maximizes the number of D in the central triatomic core. In the triatomic core, the unbounded position is preferred over the bounded position. When two D atoms are in the

outer H2 position, forming D2 is more stable than two HD. The exchange in H7+ is also

studied by monitoring the inter-nuclear distances during the DMC calculation. We didn ’t find

exchange in H7+ and D7+; however, we see this motion in partial deuterated isotopomers. The

transition state and the reaction path for this exchange are determined using both the

analytical PES and ab initio calculations. The barrier height for the exchange is 705 cm-1.

Reference:

[1] P. Barragan, R. Prosmiti, Y. Wang, J. M. Bowman, J. Chem. Phys. 2012, 136, 224302.

P64 Collisional Energy Transfer to ‘Hot’ and ‘Cold’ NO2 Molecules

Jeffrey D. Steill, Ahren W. Jasper and David W. Chandler

Sandia National Laboratories, Combustion Research Facility, Livermore, CA, USA

Collisional energy transfer of molecules is an essential aspect of chemical reactivity and maintenance of thermal equilibrium. We describe the results of recent crossed-beam experiments that investigate the distribution of energies imparted from collisions of NO2 with

Ar. By using photoexcitation of the NO2 molecule, REMPI photoionization and VMI imaging mass spectrometry methods we determine the collisional energy transfer distribution from the correlated kinetic and internal energy distribution of the NO dissociation fragment.

Results for collisions of both rotationally cold NO2 and highly vibrationally excited NO2 are presented. The intriguing differences between ground- and excited-state scattering evident in the experimental results are compared to classical trajectory scattering calculations.

P65 Two- and three-body photodissociation dynamics of ozone at 157 nm

Greg Wang

UC Berkeley

The photodissociation of ozone is investigated using fast beam photofragment

translational spectroscopy. Neutral ozone molecules are produced from the photodetachment

of O3- from 460 to 400 nm and then photodissociated at 193 nm (6.4 eV) and 157 nm (7.9 eV)

with more focus placed on 157 nm. The photofragments are detected in coincidence by a

time- and position-sensitive detector and both two- and three-body dissociation channels are

observed. Three body dissociation accounts for 3.6% of valid events at 193 nm and 19.2% at

157 nm. Since the photofragments are collected in coincidence, analysis of Dalitz plots

reveals the three-body dissociation mechanism, which appears to be concerted at both wavelengths.

P66 Vibrational Predissociation and Vibrationally Driven Isomerization of 3-Aminophenol-Ammonia

Cornelia G. Heid, Wyatt G. Merrill, and F. Fleming Crim Department of Chemistry, University of Wisconsin-Madison, Madison, WI53706

We have investigated the vibrational predissociation dynamics of the hydrogen-bonded 3- aminophenol-ammonia cluster, 3-AP-NH3. 3-AP has two stable isomers, one in which the OH group is oriented towards the NH2 group (cis-isomer), and one in which it is oriented away from the NH2 group (trans-isomer). The trans-isomer is more stable by about 0.3 kcal/mol.1 When 3-AP is supersonically expanded in the presence of ammonia, the cis- isomer disappears due to solvent-assisted isomerization which essentially traps the less stable cis-isomer in the trans-isomer well.12

In our experiments, we excite the OH stretch, or either the symmetric or antisymmetric NH stretch in the NH3 moiety of the complex. Upon vibrational excitation, the complex may then dissociate into its constituent monomers. We make use of the (1+1) REMPI scheme for 3-AP to determine the internal energy content of this fragment species.1 Our REMPI-action spectra obtained by this method show a broad, mostly unstructured feature that extends over several hundreds of wavenumbers below the electronic origin, indicating a large density of states into which the initial vibrational energy quickly flows and equilibrates. The cutoffof the broad predissociation feature also allows us to obtain a rough estimate for the dissociation energy; our data suggest that D0 for the 3-AP-NH3 complex is about 2000-2400 cm-1.

In addition to the broad predissociation feature, the REMPI-action spectrum obtained by exciting the symmetric NH stretch exhibits a sharp peak about 65 cm-1 below the well-known origin of the cis-3-AP. This difference in energy almost exactly matches the energy difference between the electronic origins of trans-3AP and trans-3-AP-NH3. We believe that this feature is a manifestation of the vibrationally driven isomerization from trans-3 -AP-NH3 to cis-3-AP-NH3. Measurements carried out at different NH3 concentrations corroborate this interpretation. We are hoping that further experiments such as IR-action spectroscopy and UV/UV-holeburning will help us conclusively assign the prominent feature in our action spectrum. It appears that the mechanism leading to its occurrence is dependent on which mode is excited, and, if it is indeed an isomerization process, that the symmetric NH stretch couples most efficiently to the isomerization coordinate, while the OH stretch and the antisymmetric NH stretch do so to a lesser degree.

1 M. Kim, S.-S. Kim, H. Kang, Y. D. Park, J. Mol. Spec. 263, 51 (2010) 2 W. Y. Sohn, M. Kim, S.-S. Kim, et al., Phys. Chem. Chem. Phys. 13, 7037 (2011)

P67 On the Mechanism for the Nonadiabatic Reactive Quenching of OH(A2E+) by H2(1E+g): The Role of the 22A State

Joseph Dillona and David R. Yarkonyb Department of Chemistry, Johns Hopkins University, Baltimore MD, 21218

Abstract A scheme for reactive electronic quenching of OH(A2E+) through collisions with H2 is

proposed, supported by electronic structure data obtained from multireference configuration

interaction wave functions. The scheme represents an insertion pathway that leads from the

initial 32A state in the reactant channel, into a valence region, where a nonadiabatic transition to

the 22A state, enabled by a 22A - 32A conical intersection seam occurs. Once on the 22A state,

insertion of HO into H2 provides access to a linking region and, after surmounting a small barrier,

to a region where the low-lying electronic states are Rydberg in character, corresponding to the

3s, 3px, 3py and 3pz states of OH3+. In the Rydberg region a deep well on the 22A potential

energy surface exists. Direct passage from the 22A state to ground state products, H2O(X1A1)+H,

is precluded by an energy barrier so that an intermediate complex can be formed on the 22A

potential energy surface. As the insertion is facilitated by rehybridization of the oxygen orbitals

from sp to sp3 in the linking region, nonplanar approach of HO to H2 is favored. The precipitous

change in electronic structure from valence to Rydberg character renders the linking region

inaccessible on the 32A potential energy surface. From the 22A state in the Rydberg region

access to the H2O + H product channel is enabled by repeated passage through a region of

appreciable 12A-22A derivative coupling or by radiative decay. This scheme supplements one in which a nonadiabatic transition from the 22A state to the 12A state in the valence region enables

both planar and nonplanar insertion paths leading directly to H2O products.

P68 Vibrational Analysis of Spectra of Hydrated Halide Clusters

Meng Huang and Anne B. McCoy

Department of Chemistry and Biochemistry, The Ohio State University

120 W. 18th Avenue, Columbus, Ohio 43210

Hydrated halide clusters provide good systems for studying the intramolecular ionic hydrogen-bond, which may help in the understanding of important processes such as transport of ions through membranes. In order to assign the argon predissociation spectra of

X-(H2O), X-(D2O) and X-(HDO) (X = Cl, Br, I),1 a reduced dimensional analysis was developed in this work. The three modes that we focus on are the two O-H(D) stretch modes and the in-plane bending mode, which is the frustrated rotation of the water molecule in the plane of the cluster. In the calculation, the O-H(D) stretch modes are treated as harmonic oscillators, while the anharmonicity of in-plane bending mode is treated explicitly as coordinate dependence of parameter in the O-H(D) stretch potential. This model is used to investigate the coupling between the three modes. The model potential and force constants are calculated using ab initio calculation with MP2/aug-cc-pVTZ(-PP) level of theory.

Qualitative agreement has been achieved between the calculated and the experimental spectra, especially the doublet structure of the O-H(D) stretch transition in the I-(H2O) spectra. Based on this, a new assignment of the combination band of in-plane bending mode and O-H(D) stretches is made. The comparison among calculated spectra of different hydrated halide clusters also show the expected agreement as the experimental spectra.

[1]Horvath S., McCoy A.B., Elliott B.M., Weddle G.H., Roscioli J. R., Johnson M. A., J.

Phys. Chem. A, 114, 1556-1568 (2010)

P69 Molecule formation by radiative association

Sergey V. Antipov, Magnus Gustafsson and Gunnar Nyman

University of Gothenburg, Sweden

Molecules are essential in the process of star formation in interstellar space and therefore it is important to know their formation and destruction rates. Due to the low densities in interstellar space, three-body collisions are extremely rare. As a result, radiative association becomes an important process for forming molecules. In this case, when two atoms collide, an emitted photon rather than a third body removes enough energy that a bound molecular state is reached. The cross sections for this process are tiny compared to ordinary bimolecular reactions.

For the calculation of radiative association rates, often semiclassical approaches have been carried out neglecting spin-orbit interactions and assuming that the rotational and total angular momenta are equal [1]. We have amended the traditional formula to make it more accurate at high energies [2]. We have also developed a classical formulation that allows us to study radiative association within a single electronic state [3], as opposed to the traditional semiclassical approaches. Here we also report time independent quantum scattering calculations.

We have applied these approximations to investigate the formation of CN, CO, SiN, SiP and HF. In the case of CO, we have investigated the formation of each of the two isotopes 12CO and 13CO through the two most important formation channels, viz.,

C(3P) + O(3P) ^ CO(A1n ) ^ CO(X1E+ ) + hv (1)

C(3P) + O(3P) ^ CO(X1E+ ) ^ CO(X1E+ ) + hv (2) and noted isotope effects of more than two orders of magnitude in the thermal rate constant at temperatures of interest in interstellar space [4] as seen in the figure below. 1 2 3 4

1e-16 [1] J. F. Babb and K. P. Kirby, The 1e-17 Molecular Astrophysics of Stars and Galaxies, Edited by T. W. Hartquist le-18 and D. A. Williams (Clarendon, Oxford, 1998). [2] M. Gustafsson, S. Antipov, J. Franz and G. Nyman; JCP, 137, 1 e-21 104301 (2012). [3] M. Gustafsson, JCP, 138, 1e-22 074308 (2013). [4] S. Antipov, M. Gustafsson, G. 1e-23. 10000 T, K Nyman; Isotope effects in formation of carbon monoxide by radiative association; MNRAS, 430, 946 (2013).

P70 Ultraviolet photodissociation dynamics of aromatic radicals

Michael Lucas, Yu Song, Jasmine Minor, Maria Alcaraz, and Jingsong Zhang

Department of Chemistry University of California at Riverside Riverside, CA 92521

and

Christopher Brazier

Department of Chemistry and Biochemistry California State University, Long Beach Long Beach, CA 90840

The ultraviolet (UV) photodissociation dynamics of two isoelectronic aromatic radicals, phenyl (C6 H5 ) and o-pyridyl (o-C5 H4N), were studied using high-n Rydberg atom time-of-flight (HRTOF) and resonance enhanced multiphoton ionization (REMPI) techniques. The phenyl radical was produced by the 193 nm photodissociation of chlorobenzene and bromobenzene and was studied in the photolysis region of 215-268 nm. The H-atom photofragment yield (PFY) spectra contain a broad peak centering around 235 nm, in good agreement with the UV absorption spectra of phenyl. The translational energy distributions of the H-atom loss product channel, P(ET)’s, peak near ~ 7 kcal/mol, and the fraction of average translational energy in the total excess energy, (fT), is in the range of 0.20-0.35 from 215-268 nm. The H-atom product angular distribution is isotropic. The dissociation mechanism is consistent with unimolecular dissociation of the ground electronic state phenyl following internal conversion. The P(ET) distribution indicates production of H + o-C6 H4 (ortho -benzyne), the lowest energy channel, via simple C-H bond fission in phenyl. The o-pyridyl radical was produced by the 193 nm photolysis of 2-chloropyridine and 2-bromopyridine and was studied in the 224-248 nm photolysis region. The PFY spectrum contains a broad peak and reveals the UV absorption feature of o-pyridyl for the first time. The P(ET) distributions peak near ~ 7 kcal/mol and fT) is nearly a constant at ~ 0.18 in the region of 224-242 nm. The H-atom angular distribution of o- pyridyl is isotropic. The dissociation mechanism is also unimolecular dissociation of hot radical after internal conversion from the electronically excited state. The P(ET)’s of o-pyridyl indicate production of H + cyanovinylacetylene, the lowest energy products; this channel proceeds via C- N bond rapture and ring opening of the o-pyridyl radical, followed by H atom loss from the ring- open intermediate. The photodissociation mechanisms of these two isoelectronic aromatic radicals will be discussed.

P71 Photodissociation Dynamics of 2-Bromoethylnitrite at 351 nm and C-C Bond Fission in the

0 -Bromoethoxy Radical Product

Lei Wang 1, Chow-Shing Lam1, Rabi Chhantyalpun2, Matt D. Brynteson1, Terry A. Miller2, and

Laurie J. Butler1

(1) Department of Chemistry, The University of Chicago, Chicago, IL 60637

(2) Department of Chemistry, The Ohio State University, Columbus, OH 43210

Photodissociations of halogenated alkyl nitrite differs from well studied alkyl nitrite. This study aims characterizing those primary photodissociated chemicals from bromoethylnitrite and the subsequent unimolecular decomposition of the nascent bromoethoxy radical formed.

We used a crossed laser-molecular beam scattering experiment and complimentary velocity map imaging to investigate the primary and secondary photodissociation channels of bromoethylnitrite at 351 nm. Only the O-NO bond fission channel forming the bromoethoxy radical and NO, no HBr photoelimination, was detected upon 351 nm photoexcitation. The subsequent decomposition of the highly vibrational excited bromoethoxy radical to formaldehyde + CH2Br was also investigated.

P72 Single microdroplet techniques for rapid profiling of solution-phase photochemistry

Philip J. Tracey, Bartholomew S. Vaughn, Chris S. Hansen, and Adam J. Trevitt

School of Chemistry, University of Wollongong, Australia

[email protected]

Here we present new techniques that combine on-demand microdroplet generation with laser photolysis. Single microdroplets (diameter ~40 pm, typically MeOH/H2O) containing photolytic precursors (~10 pM) are irradiated with a UV laser pulse and the droplet is then probed by either a second laser4 or using an in-house designed HV needle- based desorption electrospray mass spectrometry (see figure below). Using these techniques we can monitor laser-induced radical chemistry that occurs in solution. The mass spectrometry-based experiment allows a detailed and rapid survey of solution photochemistry. Single droplets are laser irradiated and analyzed one at a time; each droplet is a fresh liquid vessel that is available for photolysis and the MS analysis. Running at 10 Hz, we can profile thousands of liquid photolysis experiments in minutes. Two single droplet mass spectra of a solution containing 4-iodoanilinium (10 pM) is shown below both with and without interaction with a UV laser pulse prior to droplet desorption electrospray. It clearly reveals the photo-induced products. We have also explored benzyl radical precursors and then extend our studies to pyridine and quinoline to probe the UV laser-initiated chemistry in solution. In this presentation we discuss our latest results exploring these techniques.

No UV laser irradiating the droplet O

Droplet generator

Mass spectromete inlet Droplet -., With UV laser irradiating the droplet O

+2 kV needle UV laser

50 100 150 200 250 m/z

4 B. S. Vaughn, P. J. Tracey and A. J. Trevitt, Chem. Phys. Lett. 551, 134 (2012)

P73 Target Mass Dependence of Atom-Diatom Rovibrational Energy Transfer

Ramesh Marhatta and Brian Stewart ([email protected] ) Department of Physics, Wesleyan University, Middletown, CT 06459 Kirk Peterson Department of Chemistry, Washington State University, Pullman, WA 99164

Numerous simple models of vibrational energy transfer have been devised. Based with few exceptions on collinear dynamics [1], these models attempt to describe the dependence of the vibrational energy transfer process on variables such as *mass; * vibrational frequency; *temperature or collision energy; * initial state. But it may be that collinear dynamics cannot capture essential features of vibrationally inelastic scattering in certain cases. We recently reported [2,3] that vibrational energy transfer in light diatomic systems can be dominated by side impacts rather than collinear impacts owing to the interaction of vibration and rotation in these systems.

In an effort to determine how widespread this phenomenon is, we have carried out an experimental investigation of rovibrational energy transfer in the system

Li2 A1E+u (v = 2; jt = 3) + X ^ Lb A1E+u (v + Av; jt + A/) + X; with X equal to He, Li, Ne, Ar, Kr, and Xe. The result is a data set of over 800 absolute level- resolved rate coefficients that enable us to test simple models of vibrational energy transfer and to probe the scope of the previously-studied side-impact phenomenon.

We report the results of our comparison of these simple models with the data, as well as our efforts to extend a recent two-dimensional impulsive model [4] to three dimensions. This model allows for rotational excitation as well as vibrational excitation and may lead to an approach that can encompass the main features we see in our data. Results of classical trajectory calculations on ab initio potential surfaces for X = Ne and Xe are also reported and compared with the data. 1 2 3 4

1. J. T. Yardley, Introduction to Molecular Energy Transfer (Academic Press, New York, 1980). 2. B. A. Stewart, T. N. Stephens, B. A. Lawrence, and G. C. McBane, J. Phys. Chem. 114, 9875 (2010). 3. A. Billeb and B. Stewart, Chem. Phys. Letters, 247, 433 (1995). 4. Azriel, V. M. Rusin, L. Y. and Sevryuk, M. B. Theor. Chim. Acta 87, 195 (1993).

P74 Spectroscopic Characterization of Reactive Intermediates Relevant to Next-Generation Biofuels

NathanaelM. Kidwell,1 Vanesa Vaquero Vara,1 ThomasK. Ormond,2’3 Grant T. Buckingham2,3 Di Zhang, 1 Deepali N. Mehta-Hurt,1 Joseph A. Korn, 1 John F. Stanton, 4 G. Barney Ellison,2 Brian C. Dian,1 and Timothy S. Zwier1

1 Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, U.S.A. 2 Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, U.S.A. 3 National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401, U.S.A. 4 Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712, U.S.A.

Diminishing fossil fuel reserves and global climate change have spurred great interest in discovering a carbon-neutral, renewable energy source that will meet projected energy needs. Biomass-derived fuels possess these requirements, however, little information is available to accurately describe the combustion pathways of promising biofuels, which often involve reactive intermediates with unique chemical reactivity and spectral properties. Synthesized from cellulose, one such promising biofuel candidate is 2,5-dimethylfuran (see figure) which readily forms the 5-methyl-2-furanylmethyl (5M2F) radical upon bond dissociation. Utilizing mass-resolved jet spectroscopy combined with an electrical discharge, the electronic and infrared spectral signatures were obtained for 5M2F. In particular, the two-color resonant two-photon ionization (2C-R2PI) spectrum reveals its intriguing excited state properties and benzyl-like electronic structure. Additionally, a resonant ion-dip infrared (RIDIR) spectrum in the alkyl CH stretch region was recorded, probing the ground-state conformation of 5M2F. Using a scheme in which infrared depletion occurs between excitation and ionization steps of the 2C-R2PI process, analogous infrared spectra in D1 were also obtained, probing the geometry and response of the CH stretch fundamentals upon electronic excitation. Here, the infrared spectra report on the strong torsion-vibration coupling between the CH stretch vibrations and the n-network from the furan ring. Chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy has proven to be a well-suited technique for the rapid study and spectral identification of molecular species due to its ultra-broadband capability and excellent specificity to molecular structure from high-resolution rotational transitions. Additionally, a flash pyrolysis (hyperthermal) reactor has the attractive advantage of producing high reactive intermediate product densities in a pulsed supersonic expansion with a short residence time compared to conventional pyrolysis. Used in tandem, CP-FTMW spectroscopy with a hyperthermal reactor is a novel method to characterize important intermediates on the reaction surface of a precursor. Preliminary results will be presented where we are utilizing the exceptional resolution of the CP-FTMW spectrometer to provide insight into the molecular structure of cyclopentadienone, an anti­ aromatic reactive intermediate found to be ubiquitous in biomass pyrolysis.

m/z=96 m/z=95 2,5-Dimethylf uran 5-Methyl-2-f uranylmethyl On the Photodissociation of Phenol: A Quasi-Diabaic Representation the 1,2,31A Adiabatic Electronic Potential Energy Surfaces Coupled by Conical intersections including all 33 internal coordinates. Xiaolei Zhu , David R. Yarkony Johns Hopkins University

An algorithm previously introduced to represent global adiabatic electronic potential energy surfaces coupled by conical intersections in a terms of coupled diabatic states in tetraatomic and pentaatomic molecules is extended to treat larger molecules. The flexibility in the choice of coordinates enables the extended algorithm to describe molecules where some portions dissociate while the remainder can undergo significant internal motion. The coupled potential energy surfaces required to describe the photodissociation of phenol, C6 H5 OH+ hv -> C6 H5 OH* -> C6 H5 O + H, are reported. The ground state and lowest two excited states are considered, both near equilibrium and prefulvenic structures are described.

P76 Crossed-beam studies of the dynamics of the 18O(1D) + C16 O oxygen isotope exchange reaction and implications for non-mass-dependent oxygen isotope effects in bulk photochemistry experiments

Armando D. Estillore,1 Bing Jin,2 Tim Huang, 2 Lauren Garofalo, 1 Mica Smith, 1 Yuan T. Lee,2 Kristie A. Boering, 1,3 and Jim Jr-Min Lin2

department of Chemistry, University of California, Berkeley, CA 94720, USA 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan 3 Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA

We report the dynamics of oxygen isotope exchange reactions between 18O(1D) and carbon monoxide with the use of crossed atomic and molecular beams employing mass spectrometric detection of the C18O products. The reaction is initiated by photolysis of 36 O2 at 157 nm, which generates 18O(1D) atoms that react with CO at a collision energy of 8.2 kcal/mol. Both quenching and nonquenching isotope exchange channels are observed. The electronic quenching channel results in a forward-backward symmetric angular distribution, indicating that this pathway proceeds via a long-lived 18OCO* complex. The nonquenching channel, on the other hand, shows slightly forward-scattered products, indicating a direct direction via a short-lived 18OCO* complex. The branching ratio for these two channels (quenching:nonquenching) is 0.28:0.72 at a collision energy of 8.2 kcal/mol. Experiments at a lower collision energy at 5 kcal/mol are currently underway. Applications of these dynamics results to understanding mass-dependent and non-mass-dependent isotope effects relevant for bulk photochemical laboratory experiments and the atmosphere will also be discussed.

P77 NuACQ: Realizing native megapixel velocity map imaging with programmable USB-2.0

interfaced CCD cameras

Michael B. Doyle, Chamara Abeyasera, and A. G. Suits

Department of Chemistry, Wayne State University, Detroit, MI 48202

We introduce a powerful new approach to data acquisition for velocity map imaging

experiments that employs industrial USB-2.0 interfaced digital CCD cameras controlled by

NuACQ — a stand-alone windows executable of our own design. These devices are

relatively inexpensive and have a number of relevant advantages over standard video

cameras. Many models facilitate the accumulation of unprocessed video frames having native

megapixel resolution at acquisition rates of nearly 30 Hz. Alternatively, by summing the

centroids of regions of connected pixels, one may achieve accumulated centroid ion images with resolutions of 4 megapixels or more after interpolation. Further, digital CCD cameras

may be integrated with greater ease into a variety of experimental setups. As the cameras

transmit SVGA data over the USB interface, framegrabbers are unnecessary. Some may also be controlled by an external digital logic signal giving them great utility in scenarios that

require complex timing, event sequencing, and synchronization. Our NuACQ data

acquisition package is provided free of charge for academic use. Software development kits

for creating “machine vision” systems are also widely available for users requiring further

extensibility.

P78 Rydberg Tagging of Spin-Polarized Hydrogen Atoms: HBr Photodissociation

Bernadette M. Broderick 1, Yumin Lee1, Michael B. Doyle 1,

Oleg S. Vasyutinskii2, and Arthur G. Suits1

department of Chemistry, Wayne State University, Detroit, MI 48202 2Ioffe Institute, Russian Academy of Sciences, St. Petersburg, 19401 Russia

Rydberg tagging is a widely used probe of photodissociation and scattering that offers unmatched velocity resolution and sensitivity for reactions giving H atom products. We show a simple modification of the method that allows for simultaneous detection of the direction of the H atom spin. This offers a new window into the dynamics of the numerous dissociation or scattering processes giving H atoms as products. We demonstrate the approach in photodissociation of HBr at 213 nm. H atom spin polarization is seen arising from coherent dissociation on multiple potential surfaces for both linear and circularly polarized dissociation light. The results are in good agreement with previous theoretical predictions.

26 28 30 32 Flight Time (gs)

Figure 2. Time-of-flight spectra for H products from 213nm photodissociation of HBr by circularly polarized photolysis light probed with a circularly polarized tagging laser. Red and black curves correspond to changing dissociation laser helicity. The slower peak associated with Br* production shows substantial H atom spin polarization.

P79 Relative Efficacy of Vibrational vs. Translational Excitation in Promoting Reactivity: A Sudden Vector Projection (SVP) Model

Bin Jiang and Hua Guo* Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131

Mode selectivity, namely different efficacies of various degrees of freedom (DOFs) in promoting reactivity, represents a fundamentally important and actively studied question in chemistry.1-2 To understand the energy disposal in simple atom-diatom reactions, Polanyi proposed a set of rules that govern the relative efficacy of vibrational vs. translational excitation in promoting reactivity.3 However, the Polanyi’s rules are inadequate in predicting mode selectivity in polyatomic reactions, in which many vibrational DOFs are involved. In order to extend Polanyi's rules beyond atom-diatom reactions, we have proposed a Sudden Vector Projection (SVP) model,4 in which the relative efficacy of a particular motion can be estimated by the projection of the corresponding normal mode vector onto the vector representing the reaction coordinate, e.g. the eigenvector with an imaginary frequency at the transition state. The application of the SVP model to several prototypical atom-diatom reactions has demonstrated its general consistency with the Polanyi’s rules . In addition, the SVP model has been applied to polyatomic reactions, that, in particular, those involving H2O and CH4. One of the most intriguing experimental observations, e.g. the comparable efficacies of asymmetric and symmetric stretch modes, is predicted by SVP. The overall mode and bond selectivities in several gas phase and surface reactions can also be understood within this model. * 1 2 3 4 * corresponding author: [email protected] References: 1 R. N. Zare, Science 279, 1875 (1998). 2 F. F. Crim, Proc. Natl. Acad. Sci. USA 105, 12654 (2008). 3 J. C. Polanyi, Acc. Chem. Res. 5, 161 (1972). 4 B. Jiang and H. Guo, J. Chem. Phys. 138, 234104 (2013).

P80 Time resolved photoionization of helium nanodroplets via a femtosecond XUV pump and

an infrared or ultraviolet probe.

Michael Ziemkiewicz, Camila Bacellar, Stephen Leone, Oliver Gessner, and Daniel Neumark

Lawrence Berkeley National Lab and University of California, Berkeley

Helium nanodroplets consisting of ~106 atoms and with a radius of approximately 40 nm, have proven to be a fascinating system in which to study a wide variety of fundamental physical problems involving atomic and electronic motion. Soon after their formation, they experience evaporative cooling down to temperatures of ~ 0.4 K, meaning that they provide a unique opportunity to study dynamics in a superfluid environment. In our experiment, we start by electronically exciting the cold droplets with a burst of XUV radiation whose pulse duration is ~ 30 fs and which is produced by high harmonic generation. The photon energy of 24 eV is chosen to be lower than that needed to remove an electron from a gas phase helium atom but above the 23.1 eV ionization potential of the droplets themselves. Since this is an indirect process yielding only very low energy electrons (< 10 meV), a variety of interesting dynamics must be taking place after initial electronic excitation. It is these as yet unexplained relaxations which we directly observe using a second femtosecond laser pulse with wavelength of either 400 nm or 800nm, either of which is sufficient to surpass the atomic IP when combined with the XUV pump energy. In this talk, we present new time domain results for this system. The electrons emitted due to pump-probe photoionization from the droplets are resolved into three distinct energy bins i) an intense “ZEKE” peak with energy less than 10 meV, energetically identical to electrons emitted by one-photon ionization, ii) a low energy feature spanning the range of 0 to 1 eV, and iii) a set of high energy electrons with energies ranging from 1 eV up to hv for the probe laser (3.2 eV in the case of the 400 nm beam). By varying the time delay between the XUV pump and the IR or UV probe, a rather simple dynamical relationship is revealed between the latter two features. Namely, the high energy feature grows in with the instrument response function of the experiment but then decays with a timescale of 270 ± 30 fs while the lower energy feature grows in on a timescale of ~ 270 fs before decaying on a picosecond timescale. The shared lifetime for growth versus decay for these populations is suggestive of a well-defined transition occurring within the nanodrop let’s rather comp lex electronic structure. The nature of this change is discussed in terms of the various channels available for energy loss from the initially excited droplet state. These include purely electronic relaxation from one Rydberg band to another as well as solvent relaxation consisting of the formation of a “Rydberg bubble ” around the electronically excited atom .

P81 Spectroscopic Studies of Gas-Phase Ionic Liquids

Russell Cooper, Alex Zolot, Jaime Stearns Air Force Research Laboratory, Space Vehicles Directorate Kirtland AFB, NM

The Air Force is seeking new fuels to replace toxic hydrazines, commonly used in satellite thrusters, and to serve as the emitted material in electric propulsion systems. Ionic liquids (ILs) are potential candidates for both. However, selecting the best cation-anion combination for each thruster design, or for use as a duel fuel is a challenging problem. Calculations of ILs are not sufficiently accurate to be used predictively. Our research focuses on using spectroscopy of gas phase ionic liquids in order to asses various computational methods. We present here initial UV and IR spectroscopy of [EMIM]+[TF2N]- ion pair, a model ionic liquid. We use vibrational spectroscopy to probe the interaction between the cation and the anion and discuss the various forces that influence the structure of the molecule and consequently the vibrational modes. Comparison to various levels of theory broadens our understanding of the experimental results and lays the basis for which levels of theory are needed to accurately model ILs.

P82 Participants

Beck/Rainer [email protected]

Boering/Kristie [email protected]

Booth/Ryan [email protected]

Bowman/Joel [email protected]

Briles/Travis [email protected]

Broderick/Bernadette [email protected] .edu

Brynteson/Matthew [email protected]

Case/Amanda [email protected]

Chitsazi/Rezvan [email protected]

Clary/David [email protected]

Conte/Riccardo riccardo.conte@ emory .edu

Continetti/Robert [email protected]

Cooper/Russell [email protected]

Costen/Matthew [email protected]

Crim/Fleming [email protected]

Czako/Gabor [email protected]

Daluz/Jennifer [email protected]

Dawes/Richard [email protected]

Dey/Arghya [email protected] .edu

Dillion/Joseph [email protected]

Dong/Wenrui wrdong@stanford. edu

Doyle/Michael [email protected] Dunning/Greg [email protected]

Dzugan/Laura [email protected]

Eisfeld/Wolfgang wolfgang .eisfeld@uni -bielefeld.de

Estillore/Armando [email protected]

Fernando/Ravin [email protected] .edu

Gichuhi/Wilson [email protected]

Grubb/Michael chmpg@bristol .ac.uk

Gunina/Anastasia [email protected]

Guo/Hua [email protected]

Hase/William [email protected]

Heazlewood/Brianna [email protected]

Heid/Cornelia [email protected]

Honvault/Pascal [email protected]

Hornung/Balazs [email protected]

Huang/Haifeng [email protected]

Huang/Meng [email protected]

Hutson/Jeremy M [email protected]

Jackson/Bret [email protected]

Jiang/Bin [email protected]

Jin/Bing [email protected]

Joalland/Baptiste [email protected] .edu

Kaiser/Ralf [email protected]

Kamarchik/Eugene [email protected] Kidwell/Nathanael [email protected]

Kieda/Ryan [email protected]

Kroes/Geert-Jan [email protected]

Krylov/Ann [email protected]

Lahankar/Sridhar slahankar@ chemi stry .montana.edu

Lam/Chow-Shing [email protected]

Lam/Thanh [email protected]

Lancaster/Diane [email protected]

Lee/Yumin [email protected] .edu

Lehman/Julia [email protected]

Lester/Marsha [email protected]

Lewandowski/Heather [email protected]

Li/Wen [email protected]

Liang/Tao [email protected]

Lineberger/Carl W. [email protected]

Liu/Hanchao [email protected]

Liu/Kopin [email protected]

Livermore/David [email protected]

Lolur/Phalgun [email protected]

Lu/Yu-Ju [email protected]

Lucas/Michael mluca001@ucr. edu

Mancini/John [email protected]

Mandy/Margot [email protected] Manthe/Uwe uwe .manthe@uni -bielefeld.de

Marshall/Brooks brooksm [email protected]

Marti/Salvador Montero [email protected]

Matsika/Spiridoula [email protected]

McKendrick/Kenneth [email protected]

Merrill/Wyatt [email protected]

Minton/Donna [email protected]

Minton/Tim [email protected]

Morales/Jorge A. [email protected]

Murray/Vanessa [email protected]

Nelson/Dan [email protected]

Nesbitt/David [email protected]

Neumark/Daniel [email protected]

Nyman/Gunnar [email protected]

Opoku-Agyeman/Bernice [email protected]

Orr-Ewing/Andrew [email protected]

Osborn/David [email protected]

Osterwalder/Andreas [email protected]

Perry/David [email protected]

Petit/Andrew [email protected]

Preston/Thomas tj [email protected]

Qu/Chen [email protected]

Ray/Amelia [email protected] Reisler/Hanna [email protected]

Roesch/Daniel daniel.roesch@unib as.ch

Roy/Pierre-Nicholas [email protected]

Sage/Alan alan.sage@b ristol .ac.uk

Sanov/Andrei [email protected]

Scoles/Giacinto [email protected]

Sevy/Eric [email protected]

Shapero/Mark [email protected]

Shi/Yuanyuan [email protected] .edu

Sneha/Mahima [email protected]

Steill/Jeffrey [email protected]

Stewart/Brian [email protected]

Suits/Arthur [email protected]

Sun/Zhigang [email protected]

Tkac/Ondrej [email protected]

Trevitt/Adam [email protected]

Truhlar/Donald [email protected]

Tully/John [email protected] van de Meerakker/S. [email protected]

Van Hemert/Marc [email protected]

Volpa/Ethan [email protected]

Wagner/Al [email protected]

Wang/Gregory [email protected] Wang/Lei [email protected] .edu

Wang/Xiaohong [email protected]

Wang/Yimin [email protected]

Weichman/Marissa [email protected]

Welsch/Ralph [email protected]

Westermann/Till [email protected]

Willitsch/Stefan [email protected]

Wodtke/Alec [email protected]

Xu/Hong [email protected]

Xu/Xuefel [email protected]

Yang/Ke yang [email protected]

Yang/Xueming [email protected]. cn

Yarkony/David [email protected]

Zhu/Xiaolei [email protected]

Ziemkiewicz/Michael [email protected]

Zuev/Dmitry [email protected]

Zutz/Amelia [email protected]

Zwier/Timothy zwier@purdue .edu

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