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European Conference on the Dynamics of Molecular Systems Book of Abstracts

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European Conference on the Dynamics of Molecular Systems Book of Abstracts European conference on the dynamics of molecular systems Book of abstracts Department of Chemistry Jesus College University of Oxford 1 2 Plenary talks 3 PLENARY TALK P1 Imaging studies of inelastic collisions David H. Parker Dept of Molecular and Laser Physics, IMM, Radboud University, Nijmegen, the Netherlands. E‐mail address: [email protected] State-to-state imaging studies of the interaction of small molecules including O2,H2O, OH, CO and ammonia with H2 and with He will be described. These molecules are prominent components of molecular interstellar matter. In order to extract quantitative information on these molecules from telescope spectra, models are employed that depend critically on the rates of rotational energy exchange due to collisions with molecular hydrogen and helium. Collision rates are currently determined by theory from the multidimensional Potential Energy Surface (PES) describing the interaction of H2O and H2 [1] or He [2] and OH with H2 [3], or He. Our velocity map imaging [4] measurements of state-to-state differential and relative integral cross sections of rotational inelastic collisions, also as a function of collision energy, are used to test these PESs. For the H2O/H2, He system experiment is compared with state-of-the-art theoretical calculations by the group of L. Wiesenfeld (Grenoble) [5]. Our studies of astrochemistry relevant small molecules with the collision partners He and H2 at collision energy relevant to that of the interstellar media should place the theoretically determined PESs and the collision rates extracted from the PES on a firmer basis. References 1. P. Valiron M. Wernli, A. Faure, L. Wiesenfeld, C. Rist, S. Kedžuch, J. Noga, J. Chem. Phys. 129 134306 (2008). 2. J. Brudermann, C. Steinbach, U. Buck, K. Patkowski , R. Moszynski, J. Chem. Phys. 117 11166 (2002). 3. A. R. Offer, M. C. van Hemert, J. Chem. Phys. 99 3836 (1993). 4. A.T.J.B. Eppink, D. H. Parker, Rev. Sci. Instr. 68 3477 (1997). 5. C.-H. Yang, G. Sarma, J.J. ter Meulen, D. H. Parker, G. C. Mc Bane, L. Wiesenfeld, A. Faure, Y. Scribano, N. Feautrier, J. Chem. Phys. 133, 131103 (2010). 4 PLENARY TALK P2 Electronic nonadiabaticity in collisional quenching of OH radicals Millard H. Alexander and Jacek Klos University of Maryland, College Park, USA Paul J. Dagdigian The Johns Hopkins University, Baltimore, USA The interaction of OH in its first electronic excited state (A+) with noble gases has provoked a long and fruitful interaction between experiment and theory. There exists a deep, angularly- constricted well in both (OHM and HOM) linear geometries. For interactions with Kr, this well is deep enough to render the crossing with the two potential energy surfaces which correlate with ground state [OH(X)]+Kr products accessible even at low collision energies. Evidence of this quenching is seen in recent results from the groups of Brouard and Aoiz (Oxford and Madrid) and Lester (Pennsylvania). The nonadiabatic couplings responsible for this quenching arise from spin-orbit coupling as well as the mixing between the OH(A+) Kr state and the A’ component of the OH(X)Kr state. The dependence on geometry of these terms, as well the potential energy surfaces themselves, will determine the magnitude of the cross section for electronic quenching, and, more subtly, the distribution of the quenched products among the accessible vibrational, rotational, spin-orbit, and -doublet states. We will report on progress in obtaining a full ab initio description of the potential energy surfaces and couplings, and on using these in fully-quantum simulations of the electronically non-adiabatic scattering. 5 PLENARY TALK P3 Attosecond time-resolved molecular dynamics Marc Vrakking Max-Born Institute, Max-Born Straße 2A, 12489 Berlin Using attosecond light sources based on high-harmonic generation (HHG), pump-probe experiments can be performed where electron dynamics is studied on its natural timescale, providing insight into the fundamental role that electrons play in photo-induced processes. In my talk I will present some of the first applications of these techniques in molecular science, focusing on two-color experiments where several small molecules were exposed to a sequence of one or more attosecond pulses and an infrared field. Among other things, I will present experiments where attosecond pulses probe the electronic re- arrangement that occurs in neutral molecules and their single-ionized counterparts, under the influence of a moderately strong IR field. These experiments pave the way to the observation of time-resolved electron dynamics in more complex molecules. 6 PLENARY TALK P4 Molecular processes in space: from interstellar clouds to planets Ewine F. van Dishoeck Leiden Observatory, Leiden University, the Netherlands The space in between the stars is not empty but filled with a very dilute gas in which new stars and planets can form. In spite of the extremely low temperatures and densities, a surprisingly rich and interesting chemistry occurs in these interstellar clouds, as evidenced by the detection of more than 150 different molecules. The observed composition points to a chemistry that is far out thermodynamic equilibrium and is determined by the kinetics of the atomic and molecular processes. Early astrochemical models considered primarily gas-phase processes such as radiative association, dissociative recombination, photodissociation, and ion-molecule reactions. In recent years, it has become clear that processes on the surfaces of dust grains play a more important role than thought before in explaining the observed composition. Recent laboratory and theoretical results on selected processes will be reviewed, with a focus on photon-induced processes. Special attention will be paid to reactions involving water and to new data at THz frequencies from the Herschel Space Observatory. 7 PLENARY TALK P5 CHEM-ICE-TRY Solid state pathways towards molecular complexity in space Harold Linnartz Sackler Laboratory for Astrophysics, Leiden Observatory, University of Leiden, PO Box 9513, NL 2300 RA Leiden, the Netherlands *E-mail: [email protected] Icy dust grains in space act as catalytic surfaces onto which new molecules form. These molecules – both small, abundant as well as complex (‘prebiotic’) species – are synthesized in energetic and non-energetic processes: UV and cosmic ray irradiation and H-atom addition reactions. In order to study such processes quantitatively dedicated laboratory experiments are performed that simulate the conditions in the inter- and circumstellar medium [1-4]. The outcome is used to compare with astronomical observations and as input for astrochemical models. In parallel, the experiments provide information on the involved molecular processes. This talk gives answer on the questions how water forms in space, how complex species are formed, whether chemistry in space may be wavelength dependent, and which parameters are at play in chem-ice-try, the study of reactions in interstellar ices. The derived reaction scheme for water formation in space. Details are available from [1]. References [1] H.M. Cuppen, S. Ioppolo, H. Linnartz, PCCP, 12 (2010) 12077. [2] K.I. Öberg, R.T. Garrod, E.F. van Dishoeck, H. Linnartz, A&A, 504 (2009) 891. [3] S. Ioppolo, Y. van Boheemen, H.M. Cuppen, E.F. van Dishoeck, H. Linnartz, MNRAS, 413 (2011) 2281. [4] E. Congiu, S. Ioppolo, F. Dulieu, H. Chaabouni, S. baouche, J.L. Lemaire, C. Laffon, P. Parent, T. Lamberts, H. Cuppen, H. Linnartz, ApJL, 750 (2012) L12. 8 PLENARY TALK P6 Intersystem crossing dynamics in polyatomic multichannel reactions of oxygen atoms with unsaturated hydrocarbons Piergiorgio Casavecchia Dipartimento di Chimica, Università degli Studi di Perugia, 06123 Perugia, Italy *E-mail: [email protected] Comparisons between experimental cross sections and theoretical predictions on ab initio potential energy surfaces (PESs) for benchmark 3-atom, 4-atom, and recently non-complex forming 5-atom reactions have greatly advanced our understanding of chemical reactivity over the last decade. Nonetheless, experimental and theoretical investigations of the dynamics of more complex polyatomic reactions, with numerous competing product channels, e.g., 3 O( P)+C2H4, still represent a major challenge for both experiment and theory. Experimentally, a major challenge is to study all open channels with the same degree of accuracy and under the same experimental conditions. This is a prerequisite to identify the primary products and determine their relative importance (branching ratios, BRs). A “universal” detection method to interrogate all product channels on the same footing, such as mass-spectrometry (MS), is required and this can be best pursued in crossed molecular beam (CMB) experiments [1]. CMB- MS studies of these reactions have recently become feasible using “soft” ionization detection by tunable low energy electrons [2,3] or VUV synchrotron radiation [4]. Theoretically, the development of full-dimensional PESs is needed on which to perform dynamic (quasiclassical trajectory-QCT) calculations, and this is now becoming practical [3]. For reactions with the added complexity of nonadiabatic coupling (intersystem crossing, ISC) of PESs, the challenge to theory and experiment is perhaps at its highest level. In this talk, I will highlight and discuss our recent efforts to unravel the dynamics of polyatomic nonadiabatic multichannel reactions. In particular, by studying in crossed beams the reaction dynamics of O(3P) with a variety of unsaturated hydrocarbons (acetylene, ethylene [3,5], allene [6] and methylacetylene), central issues such as the variation with Ec of the dynamics, BRs and extent of ISC from triplet to singlet PESs are examined, as well as the dependence of ISC on molecular complexity and structure [3,5,6]. The experimental results are rationalized in the light of the underlying PESs and compared with statistical predictions and/or QCT surface-hopping calculations on coupled, full-dimensional ab initio triplet and singlet PESs, providing an important test ground for theoretical dynamics methods that can be used widely to study ISC dynamics. References [1] P. Casavecchia, K. Liu, and X.
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