RSC Spectroscopy and Dynamics Group Meeting 2020

University of Warwick 6th – 8th January 2020

We would like to extend our thanks to the RSC and all of our sponsors for their generous support of this year’s Spectroscopy and Dynamics Group meeting. Please show your support for our sponsors by visiting their trade stands during the coffee breaks and Tuesday’s poster session.

Programme

All presentation sessions will take place in Meeting Room 2 inside the Radcliffe Conference Centre.

Monday 6th January 16:00 - 18:00 Arrival and Registration

18:00 - 19:00 Dinner Dining Room

Session 1 Chair: Caroline Dessent 19:00 - 19:05 Welcome Vas Stavros (Warwick) 19:05 - 19:50 Invited tutorial talk Helen Fielding (UCL) 19:50 - 20:35 Invited tutorial talk Tom Penfold (Newcastle) 20:35 - 21:35 SDG AGM Meeting Room 2

Tuesday 7th January 07:00 - 08:30 Breakfast Dining Room*

Session 2 Chair: Michael Staniforth 09:00 - 09:45 Invited talk David Osborn (Sandia NL) 09:45 - 10:05 Contributed talk David Kemp (Nottingham) 10:05 - 10:25 Contributed talk Klaudia Gawlas (UCL) 10:25 - 10:45 Contributed talk Preeti Manjari Mishra (RIKEN)

10:45 - 11:15 Tea/Coffee Lounge

Session 3 Chair: Jutta Toscano 11:15 - 12:00 Invited talk Sonia Melandri (Bologna)

12:00 - 12:20 Contributed talk Maria Elena Castellani (Durham) 12:20 - 12:40 Contributed talk Javier S. Marti (Imperial) 12:40 - 13:00 Contributed talk Conor Rankine (Newcastle)

13:00 - 14:15 Lunch Dining Room

Session 4 Chair: Nat das Neves Rodrigues 14:15 - 14:35 Contributed talk Jacob Berenbeim (York) 14:35 - 14:55 Contributed talk Thomas Wall (Imperial) 14:55 - 15:15 Contributed talk Ayse Duran (Nottingham) 15:15 - 15:35 Contributed talk David Heathcote (Oxford) 15:35 - 15:55 Contributed talk Jutta Toscano (Colorado)

16:00 - 16:30 Tea/Coffee Lounge

16:30 - 18:00 Poster session** and trade display 18:00 - 19:00 Invited Talk Bern Kohler (Ohio) 19:00 - 20:00 Conference Dinner Dining Room 20:30 - 22:00 Quiz Dining Room

Wednesday 8th January

07:00 - 08:30 Breakfast Dining Room*

Session 5 Chair: Javier Segarra-Marti 09:00 - 09:45 Invited talk Eric Vauthey (Geneva) 09:45 - 10:05 Contributed talk Alex Auty (Sheffield) 10:05 - 10:25 Contributed talk Mahima Sneha (Bristol) 10:25 - 10:45 Contributed talk Daniel Coxon (Warwick)

10:45 - 11:15 Tea/Coffee Lounge

Session 6 Chair: Mahima Sneha 11:15 - 12:00 Invited talk Julia Lehman (Leeds) 12:00 - 12:20 Contributed talk Andriana Tsikritea (Oxford) 12:20 - 12:40 Contributed talk Lea Maria Ibele (Durham) 12:40 - 13:00 Contributed talk Lingfeng Ge (Bristol)

13:00 - 14:15 Lunch Dining Room

Session 7 Chair: Stuart W. Crane 14:15 - 14:35 Contributed talk Emily Holt (Warwick) 14:35 - 14:55 Contributed talk Ecaterina Burevschi (KCL) 14:55 - 15:15 Contributed talk Matthew Rayment (UCL) 15:15 - 15:35 Contributed talk João Figueira Nunes (Lincoln) 15:35 - 15:55 Contributed talk Alice Green (Oxford)

15:55 - 16:30 Tea/Coffee Lounge 16:30 Finish

*For attendees staying at accommodation sites other than Radcliffe (i.e. Scarman and Arden), breakfast will be served in their respective dining rooms. All other meals will be served at Radcliffe for all attendees.

**Posters can be put up from 4pm on Monday (first conference day) but must be taken down by 9am on Wednesday (last conference day).

Talk Abstracts

University of Warwick 6th – 8th January 2020

Invited Tutorial Talk

Liquid-microjet UV photoelectron spectroscopy

Helen H. Fielding1,*

1 Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K. * [email protected]

In nature, light drives many important processes such as photosynthesis and vision. Light-driven processes are also important in technology, such as in nanoscale electronic devices. At the heart of all these processes are small chromophores that absorb light and, subsequently, undergo small- scale structural changes. Understanding the fundamental photophysics and photochemistry of the chromophores that determine the efficiency of light-driven processes in nature and technology is crucial for the rational design of new photomaterials for a range of applications such as photovoltaics and bioimaging. In addition to a detailed knowledge of the intrinsic electronic structures of these chromophores, it is important to have an understanding of the roles of their environments. Experimentally, the most direct way of probing electronic structure is through the measurement of binding energies using photoelectron spectroscopy (PES). Liquid-microjet UV PES is emerging as a valuable probe of the electronic structure of chromophores in solution. This tutorial lecture will include a brief review of the history of liquidmicrojet photoelectron spectroscopy and an explanation of the challenges facing UV PES of liquids. It will include a description of the design and operation of the recirculating liquid-microjet PES instrument we have built at UCL for studying samples that are available in relatively small quantities1 and illustrative liquid-microjet PES measurements of phenol2,3 and the green fluorescent protein (GFP) chromophore.

[1] J. W. Riley, B. Wang, M. A, Parkes, H. H. Fielding, Rev. Sci. Instrum., 90 083104 (2019) [2] J. W. Riley, B. Wang, J. L. Woodhouse, M. Assmann, G. A. Worth, H. H. Fielding, J. Phys. Chem. Lett., 9 678-682 (2018) [3] A. Henley, J. W. Riley, B. Wang, H. H. Fielding, Faraday Discuss., DOI:10.1039/c9fd00079h (2019)

Invited Tutorial Talk

Time-resolved Structural Dynamics

Thomas J. Penfold1

1 Chemistry- School of Natural and Environmental Science, Newcastle University

Ultrafast studies emerged with the implementation of femtosecond-picosecond linear and nonlinear optical spectroscopies and had a huge impact on our understanding of chemical reactions, biological functions and phase transitions in materials owing to their ability to probe, in real-time, the nuclear motion within these different types of systems. However, for systems of more than two the link between the optical domain spectroscopic observables and the molecular structure is ambiguous and therefore from the early days of ultrafast spectroscopy much effort was invested to develop methods that achieve both high temporal (on the femtosecond time scale) and spatial (on the order on tenths of an Angström) resolution.

Capturing the evolving geometric, electronic and spin structure during the course of a chemical reaction or biological process is the principal aim of time-resolved X-ray techniques. The advent of X-ray free electron lasers introduces a paradigm shift in terms of the temporal resolution of X-ray techniques, and offers exciting possibilities for time-resolved second-order X-ray spectroscopies and non-linear X-ray experiments. In parallel, the improved data quality is making it increasingly important to accurately simulate the fine spectroscopic details. This has been the driving force for new theoretical methods permitting a detailed interpretation of the spectra in terms of the geometrical and electronic properties of the system.

In this contribution, I will discuss some of the recent experimental and theoretical developments in ultrafast X-ray techniques and explore the new opportunities they offer.

[1] C.J. Milne et al., Coord. Chem. Rev., 277, 44-68 (2014). [2] G. Capano, et al., J. Phys. B, 48, 214001 (2015). [3] T. Katayama, et al., Nat. Comm., 10, 1-8 (2019).

Invited Talk

To Boldly Look Where No One Has Looked Before: The Surprising Story of Acetylacetone Photochemistry

I. Antonov,1 K. Voronova,2 M. W. Chen,1 B. Sztaray,2 P. Hemberger,3 A. Bodi,3 D. L. Osborn,1,* and L. Sheps1

1 Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States 2 Department of Chemistry, University of the Pacific, Stockton, California 95211, United States 3Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland * [email protected]

The absorption of light by an organic , and the subsequent pathways for energy transformation and release, are fundamental processes governing life on earth. Two of the most important electronic chromophores in organic systems are C=O bonds (carbonyl ) and C=C bonds (alkenes and polyenes). We have studied [1] the photodissociation of acetylacetone (AcAc), which exists at 300 K in the gas phase mostly as the enolone tautomer, rather than the diketo tautomer (see figure). The enolone tautomer is stabilized by both  conjugation and an internal bond. In a molecule such as this with more than one chromophore, it is interesting to consider whether AcAc’s photochemistry will be like that of a polyene or a ketone, or something different from either. Previous studies concluded that OH loss is the dominant (or only) channel when AcAc is excited in the ultraviolet at 266 or 248 nm. However, truly universal detection techniques were not used in these studies. By combining multiplexed photoionization mass spectrometery (MPIMS), threshold photoelectron photoion coincidence spectroscopy (TPEPICO), and time-resolved infrared absorption spectroscopy of OH radicals, we discovered that photodissociation of AcAc is much richer than previously presumed, and that OH production is not even energetically allowed following one-photon excitation at 266 or 248 nm. This work demonstrates the power of multiplexed, universal detection of charged particles in photodissociation studies, and lifts the veil on the photodissociation of a molecule that is both an enol and a ketone.

[1] I. Antonov, K. Voronova, M. W. Chen, B. Sztaray, P. Hemberger, A. Bodi, D. L. Osborn, and L. Sheps, Journal of Physical Chemistry A, 123 5472 (2019)

Contributed Talk

Modifications of torsional potentials in the m-fluorotoluene and m-chlorotoluene cations

D.J. Kemp,1,* A.R. Davies,1 L.G. Warner,1 E.F. Fryer1 and T.G. Wright1

1 School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK * [email protected]

The coupling of methyl torsion and vibrational motions has been the subject of a series of studies on various substituted benzenes using a combination of fluorescence and photoionization spectroscopies. These studies have shown that such coupling can be examined; this underpins the ability to understand energy dispersal, photostability, and photochemical control.

In the low internal energy region (< 350 cm-1 above the electronic origin) of both meta-fluorotoluene [1],[2] and meta-chlorotoluene [3], various interactions occur between pure vibrational states and both pure torsional levels and vibration-torsion (vibtor) combinations. Additionally in the cation, the torsional potential can be shown to undergo modification as a result of vibration-specific interactions, where the degree of the modification may be inferred qualitatively from the motion of the ring-localised atoms relative to the methyl rotor atoms.

[1] D.J. Kemp, E.F. Fryer, A.R. Davies, T.G. Wright, J. Chem. Phys., 151, 084311 (2019) [2] L.D. Stewart, J.R. Gascooke, W.D. Lawrance, J. Chem. Phys., 150, 174303 (2019) [3] D.J. Kemp, L.G. Warner, T.G.Wright, in progress

Contributed Talk

Rydberg-state-resolved resonant energy transfer in cold electric-field-controlled collisions of NH3 with Rydberg He atoms

K. Gawlas1,* and S. D. Hogan1

1 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom * [email protected]

Owing to the large size of the Rydberg electron wavefunction, atoms in Rydberg states can be extremely sensitive to collisions with other atoms and molecules. When the intervals between appropriate Rydberg energy levels exactly match those in the collision partner, energy can be resonantly transferred between the two. Since the transitions between Rydberg states with values of n > 30 typically lie in the wavenumber range between 1 and 100 cm−1, atoms in such states are, therefore, ideally suited to study energy transitions from the rotation or fine-structure intervals in neutral ground-state molecules. This has led, for example, to experimental studies of the transfer of rotational energy in NH3 to Xe Rydberg atoms [1], or the energy associated with the inversion transitions in NH3 to Rb Rydberg atoms [2]. More recently, demonstrations of electric-field-controlled resonant energy transfer in collisions of room temperature effusive beams of NH3 with He Rydberg atoms [3], or collisions of thermal gasses of NH3 with Rb Rydberg atoms [4].

Here we extend this work to translational temperatures of ~1 K by performing studies of electric- field-controlled resonant energy transfer between He atoms in the triplet 38s Rydberg state and ground-state NH3 co-moving in pulsed supersonic beams [5]. The He atoms were initially prepared 3 in the metastable 1s2s S1 level in the trailing part of the beams and the velocity slip between the heavy NH3 and the lighter metastable He was exploited to perform collision studies at centre-of- mass collision speeds of 70 m/s. Resonant energy transfer from the 38s state in He to states with

38p character were tuned into resonance with the ground-state inversion transitions in NH3 using electric fields of <15 V/cm. The energy transfer process was monitored by state-selective electric field ionisation. This work opens new opportunities to allow long-range electric dipole interactions to be exploited to regulate access to short-range chemical processes, including ion-molecule reactions [6].

[1] K. A. Smith, F. G. Kellert, R. D. Rundel, F. B. Dunning, R. F. Stebbings, Phys. Rev. Lett., 40, 1362 (1978) [2] L. Petitjean, F. Gounand, P. R. Fournier, Phys. Rev. A, 33, 143 (1986) [3] V. Zhelyazkova, S. D. Hogan, J. Chem. Phys., 147, 244302 (2017) [4] F. Jarisch, M. Zeppenfeld, New J. Phys., 20, 113044 (2018) [5] C. Amarasinghe, A. G. Suits, J. Phys. Chem. Lett., 8, 5153 (2017) [6] P. Allmendinger, J. Deiglmayr, K. Hoveler, O. Schullian, F. Merkt, J. Chem. Phys., 145, 244316 (2016)

Contributed Talk

Ion and photon induced collisional dynamics in large molecular ions

P. M Mishra1* and others2,3,4

1 RIKEN, 2-1 Hirosawa, Wako, Saitama, Japan 2 Indian Institute of Space Science and Technology, Trivandrum, India 3 Elettra-Sincrotrone Trieste, Basovizza, Italy 4 Max Planck Institute for Nuclear Physics, Heidelberg, Germany * [email protected]

Ion- or photon-induced ionization and fragmentation processes of molecular ions are of significance in a wide range of research, from fundamental molecular physics to astrophysics as well as atmospheric science. Depending on the energy of the collision process, several reaction channels such as direct ionization, fragmentation, evaporation (loss of small fragments/atoms) in large molecules can be found. These processes are extremely sensitive to the thermal energy associated with the various internal degrees of freedom of the molecule. Collective excitation is another feature which is related to the inherent stability mechanism for conjugated molecules.

I will present such processes in large molecules (polycyclic aromatic hydrocarbons and carbon- oxygen clusters) under photon and charged particle radiation impact in both room temperature as well as cryogenic temperature using a wide variety of experimental set ups. The experiments are carried out at Synchrotron facility, Electron Cyclotron Resonance facility as well as at Ion Storage Ring facility. All are special and unique in terms of their experimental plan, regime and outcomes [1-5]. The theory work performed by me to explain the above experimental results will also be discussed [6, 7].

[1] P. M. Mishra et al., Phys. Rev. A, 88, 052707 (2013) [2] P. M. Mishra et al., Nucl. Instrum. Meth. B, 336, 12-18 (2014) [3] P. M. Mishra et al., J. Phys. Chem. A, 118, 3128-3135 (2014) [4] A. P. O’Connor et al., Physical Review Letters, 116, 113002 (2016) [5] C Meyer et al. Physical Review Letter, 119, 023202 (2017) [6] P M Mishra et al., J. Phys. B: Atomic, Molecular and Optical Physics, 47, 085202 (2014) [7] P M Mishra, Computational and Theoretical Chemistry, 1068, 165-171 (2015)

Invited Talk

Hydrogen bonds and other intermolecular non-covalent interactions revealed by rotational spectroscopy

S. Melandri1,*

1 Dipartimento di Chimica G. Ciamician, Università di Bologna, Bologna, Italy * [email protected]

The nature and driving forces of intra and intermolecular non-covalent interactions can be studied to a very high degree of accuracy by free-jet rotational spectroscopy. From the detailed structural and dynamical data obtained, the site and geometry of the interaction and information on the binding energy can be inferred without ambiguity, also in the presence of conformational complexity [1,2] The questions usually addressed regard, the binding sites, the kind of established interactions, the conformational changes caused by interactions and finally the driving forces of the interactions and how they can be influenced. When applied to molecular complexes, answers to these questions allow insight into the molecular interaction process at the molecular level, bridging the gap between gas-phase and bulk properties. Through chosen examples of published [3-6] and unpublished results on molecular complexes of medium-size organic molecules formed in a supersonic expansion and characterized by rotational spectroscopy, we will show how non-covalent interactions (hydrogen bonds, weak hydrogen bonds, halogen bonds, pnicogen bonds and lp-π-hole interactions) compete to shape the conformational potential energy surface of the complexes, determine their shapes and even influence molecular reactivity. We will also show how these interactions drastically change through substitution (in particular by halogen atoms) of atoms or functional group, in this way achieving an effective tuning of the non-covalent interactions themselves.

[1] M. Becucci, S. Melandri, Chem. Rev., 116 5014 (2016). [2] I. Uriarte, S. Melandri, A. Maris, C. Calabrese, E. J. Cocinero, J. Phys. Chem. Lett., 9 1497 (2018). [3] C. Calabrese, Q. Gou, A. Maris, W. Caminati, S. Melandri, J. Phys. Chem. Lett., 7 1513 (2016). [4] L. Evangelisti, K. Brendel, H. Maeder, W. Caminati, S. Melandri, Angew. Chem., 56 13699 (2017). [5] C. Calabrese, W. Li, G. Prampolini, L. Evangelisti, I. Uriarte, I. Cacelli, S. Melandri, E. J. Cocinero, Angew. Chem., 58 8437 (2019). [6] W. Li, A. Maris, C. Calabrese, I. Usabiaga, W. D. Geppert, L. Evangelisti, S. Melandri, Phys. Chem. Chem. Phys., 21 23559 (2019).

Contributed Talk

On the stability of a dipole-bound state in presence of a molecule

Maria Elena Castellani,1,* Cate S. Anstöter1 and Jan R. R. Verlet1

1 Department of Chemistry, Durham University, DH1 3LE, Durham, County of Durham, United Kingdom. * [email protected]

Dipole bound states (DBSs) are non-valence states of anions in which the electron is bound to the molecule through the electric dipole moment of the neutral core. These states, analogous to Rydberg states in neutral molecules, have only been observed in the gas phase so far, as there is no evidence of their subsistence when surrounded by an environment. In order to investigate whether the DBS can survive in presence of another molecule, the phenolate (ph-) anion, known to present a DBS, 2, 3 is used as model. An alkyl chain of progressively increasing length (n-ph-) is attached to the molecule so that it “pokes” into the DBS. The stability of the DBS is assessed through photodetachment action spectroscopy, frequency-resolved photoelectron imaging (FR-PEI) and resonance-enhanced two-photon photoelectron imaging (R2P-PEI) 1.

Action spectroscopy measurements on n-ph- within the range of 560-600 nm show that the DBS peak can be identified in all action spectra. Nevertheless, considerable resolution loss and a blue- shift of the DBS peak are observed in function of increasing chain length. The blue-shift is explained as a consequence of an increase in electron affinity proportional to the number of carbons in the chain, as seen in the PE spectra of n-ph- recorded at 500 nm. On the other hand, the loss of resolution may indicate that, for n-ph- with longer alkyl chains, the DBS is disrupted. R2P-PEI images were recorded at the wavelength corresponding to the 0-0 transition identified in the action spectra. Perhaps surprisingly, each R2P-PEI of the images presents a second, narrow peak with photoelectron angular distribution (PAD) peaks parallel to the polarization axis, consistently with a DBS. This indicates that the DBS subsists even if there is an alkyl chain directly interacting with it.

Therefore, we can conclude that, despite the limited space available, the DBS is retained in all cases. The loss of resolution visible in the action spectra is explained as a shift in the electron binding energy (eBE) of the DBS, caused by the conformational change that the alkyl tail undergoes at 300 K.

1. M. E. Castellani, C. S. Anstöter and J. R. R. Verlet, Physical Chemistry Chemical Physics, 2019, 21, 24286-24290. 2. H. T. Liu, C. G. Ning, D. L. Huang, P. D. Dau and L. S. Wang, Angewandte Chemie-International Edition, 2013, 52, 8976-8979. 3. G. Z. Zhu, C. H. Qian and L. S. Wang, The Journal of Chemical Physics, 2018, 149.

Contributed Talk

Modelling Ultrafast Photoionisation in DNA/RNA Pyrimidine Nucleobases

J. Segarra-Martí,1,* T. Tran,1 T. A. Mackenzie,1 M. J. Bearpark1

1 Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London W12 0BZ, UK * [email protected]

Photoinduced phenomena in DNA is of interest to the scientific community due to its relation with growing healthcare concerns such as skin cancer melanoma. [1] Most studies so far have focused on the effects of low-energy UV-A/B laser pulses, as these are akin to the type of incident Sunlight radiation we are exposed to on a daily basis and trigger a number of photochemically productive reactions (mutations) in our genomic material. [2] Much less attention has been paid however to the effects of photoionisation, which refers to the process of photoinduced electron removal in the DNA chromophoric species the nucleobases, producing their cationic forms. This process is featured in the presence of higher-energy (UV-C and Alpha-particle) radiation sources or in multimeric DNA/RNA species upon UV-A/B exposure. [3] Albeit scarcely studied, cations are significantly produced in DNA and are considered to be responsible of damaging instances such as DNA cross links, base releases and single/double strand breaks known to occur upon radiation exposure .[4]

In this contribution we thoroughly simulate a range of photoionisation phenomena in DNA/RNA nucleobases (uracil, thymine, cytosine and the epigenetic 5-methylcytosine), [5,6] assessing the differences observed by initially accessing diverse cationic states, and predict their time-resolved spectral fingerprints to identify the molecular motions driving these ultrafast photo-reactions. [7] To do this we explore the deactivation channels of all low-lying accessible cationic states of both π+ and n+ character with the strongly correlated complete active-space self-consistent field (CASSCF) method. We characterise the critical molecular structures embodying the photo-process (ground, minima and conical intersections), simulate non-adiabatic molecular dynamics schemes to obtain estimates of the cation excited electronic state lifetimes and use these to model their associated time-resolved spectral fingerprints. We then combine the results obtained and connect the similarities registered across the different pyrimidine nucleobases to propose a unified ultrafast decay mechanism for all pyrimidine cations that extend previous models proposed for the singlet manifold. [8,9]

[1] F. P. Noonan et al., Nat. Commun., 3 884 (2012) [2] J. Cadet et al., Photochem Photobiol, 88 1048-1065 (2012) [3] A. Banyasz et al., Faraday Discuss., 207 181-197 (2018) [4] S. Lehnert, Biomolecular Action of Ionizing Radiation, Taylor and Francis (2008) [5] J. Segarra-Martí et al., Phys. Chem. Chem. Phys., 21 14332-14330 (2019) [6] J. Segarra-Martí et al., ChemPhotoChem, 3 856-865 (2019) [7] J. Segarra-Martí et al., Top. Curr. Chem., 376 24 (2018) [8] M. Merchán et al., J. Phys. Chem. B, 110 26471-26476 (2006) [9] A. J. Pepino et al., J. Phys. Chem. Lett., 8 1777-1783 (2017)

Contributed Talk

Teaching Spectroscopy to a Deep Neural Network: Instantaneous Prediction of Spectra via Machine Learning

C. D. Rankine,1* M. M. M. Madkhali,1 T. J. Penfold1

1 Newcastle University, Newcastle-upon-Tyne, NE1 7RU, UK * [email protected]

Deep machine learning models – mechanisms via which computers are able to extract and learn patterns represented in ‘big data’ [1,2] – have been deployed to address complex, multivariate problems in material, catalyst, and drug design, [3-5] chemical reaction prediction and optimisation, [6] and atomistic modelling; [7] they occasionally outperform chemists on these tasks! [2] At Newcastle University, we are training deep artificial neural networks (ANNs) to help spectroscopists streamline their workflow. Our ANNs are capable of making spectral simulations that presently take hours/days possible in under a second. We report the development and deployment of our first ANN based on the deep multilayer perceptron (MLP) model. Our ANN delivers instantaneous, ‘black-box’ prediction of X-ray absorption near-edge structure (XANES) spectra at the iron Kedge, bypassing the bottleneck of expensive quantum-chemical calculations. After learning how to map the relationship between the local environment of the absorbing and the corresponding XANES spectrum from a diverse set of ca. 8,000 in-sample examples, our ANN is able to predict subsequently the XANES spectra of unseen, out-of-sample materials with sub-eV accuracy on peak positions.

[1] Y. LeCun, Y. Bengio, and G. Hinton, Nature, 521, 436 (2015) [2] A. C. Mater and M. L. Coote, J. Chem. Inf. Model., 59, 2545 (2019) [3] D. Jha et al., Sci. Rep., 8, 17593 (2018) [4] Z. Zhou et al., Sci. Rep., 9, 10752 (2019) [5] J. Schmidt et al., Npj Comput. Mater., 3, 589 (2019) [6] A. Filipa de Almeida et al., Nat. Rev. Chem., 3, 589 (2019) [7] K. Schütt et al., Nat. Comm., 10, 5024 (2019)

Contributed Talk

UV Photodissociation of Protonated 4-tert-butyl-4’-meth-oxydibenzoylmethane

Jacob A. Berenbeim,1,* Natalie G.K. Wong1 and Caroline E.H. Dessent1

1 Department of Chemistry, University of York, Heslington, York, United Kingdom * [email protected]

It is well established that despite evolved biological function, prolonged and acute doses of UVA and UVB can cause dermatologic inflammation, premature aging, reactive oxygen species generation, and alter DNA to cause cancer in animals. Our group has begun studying common sunscreen molecules isolated in the gas phase to characterize their intrinsic photochemical properties.1,2 This data is sparse for gaseous sunscreens (see section 1.2.2 of the most recent review by Holt & Stavros covering molecular-beam work)3 and was non-existent for charged gaseous sunscreens until our recent involvement. We use electrospray ionization to prepare either the common ionic form, such as in the case of 2-phenylbenzimidazole-5-sulfonic acid (common name Ensulizole, PBSA) which is a negative ion under neutral solvated conditions, or protonated/deprotonated forms representative of varied pH conditions, as was the case for 2- Hydroxy-4-methoxybenzophenone (common name Oxybenzone, BP3). These ions are then isolated in a quadrupole ion trap where we perform photodepletion studies with a tuneable laser source. Photofragmentation spectra are collected in hand with the laser-ON component of the photodepletion experiment.

Here, we present the work we’ve recently done on protonated 4-tert-butyl-4’- methoxydibenzoylmethane (common/trade names Avobenzone, Parsol 1789, BD-DBM). BD-DBM is one of the most widely used UVA filters today and the dibenzoylmethane family are known to take multiple isomerization pathways following UV excitation. The aim of this work was to see whether BD-DBM could effectively be electro sprayed and measured by photodepletion in the gas phase. Furthermore, whether the protonated analogues of the chelated enol (i.e. UVA photoactive isomer) and diketone form (UVB photoactive isomer and prone to degradation) could be measured separately in the gas phase to allow for a comparison of their respective electronic spectra. Notably, we will show that the photofragment yields add insight to the photo tautomerization of BD-DBM.

1. N. G. K. Wong, J. A. Berenbeim, M. Hawkridge, E. Matthews and C. E. H. Dessent, Phys. Chem. Chem. Phys., 2019, DOI: 10.1039/c8cp06794e. 2. N. G. K. Wong, J. A. Berenbeim and C. E. H. Dessent, ChemPhotoChem, 2019, DOI: 10.1002/cptc.201900149. 3. E. L. Holt and V. G. Stavros, Int. Rev. Phys. Chem., 2019, 38, 243-285.

Contributed Talk

A new laser for vibrational spectroscopy

T.E. Wall,1,* M. Manceau,2 A. Cournol,2 H. Philip,3 A.N. Baranov,3 M.R. Tarbutt,1 R. Teissier,3 and B. Darquié2

1 Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK 2 Laboratoire de Physique des Lasers, CNRS, Université Paris 13, Sorbonne Paris Cité, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse, France 3 Institut d'Électronique, University of Montpellier, CNRS, 34095 Montpellier, France * [email protected]

The mid-infrared contains the fingerprint region, where molecules can be identified by their vibrations. While the 1 – 10 µm region is fairly well covered by available lasers, laser spectroscopy at longer wavelengths is comparatively unexplored. I present a new distributed feedback (DFB) quantum cascade laser (QCL) that operates at 17 µm, the first room-temperature CW DFB QCL to operate at this long wavelength [1].

QCLs are widely-tunable, potentially very narrow-linewidth lasers, with a range of applications in miniaturized chemical sensors as well as fundamental physics. I will discuss the applications of this new laser to atmospheric sensing, quantum science with ultracold molecules, and testing the stability of fundamental constants. I will describe our characterization of this laser, including measurements of its spectral range, frequency noise and linewidth. We have also demonstrated its capabilities by performing spectroscopy of the v2 fundamental mode of N2O, including the most precise investigation of pressure broadening in this mode. Finally, I will describe the opportunities for quantum state control and precise spectroscopy of ultracold CaF.

Figure: (red) measured absorption spectrum of the v2 fundamental mode of N2O; (black) stick spectrum calculated using HITRAN.

[1] H.N. Van et al., Photonics 6, 31 (2019)

Contributed Talk

Velocity Map Imaging using a 3D Imaging Detector

A. T. Duran,1,2,* T. M. Conneely,2 J. Milnes2 and I. Powis1

1 School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK 2 Photek Limited, 26 Castleham Road, St. Leonards-on-sea, TN38 9NS, U.K * [email protected]

Many problems in molecular dynamics require the simultaneous measurement of a particle's speed and angular direction in coincidence with its internal energy. The spatial distribution of ejected following a photoionization process provide great information on the target and on the newly created ion. Photoelectron Angular Distributions (PADs) are measured frequently to get information on structures and distributions of molecules and on dynamics between them. The acquired knowledge about the behaviour of molecules can then be used to develop new shapes of drug molecules to control the way a medicine works which is valuable in medicine and to produce new materials with improved specifications. Progress in this area is highly technologically driven, requiring ever more sophisticated light sources and faster detectors.

This work is being carried out between Photek Ltd UK and University of Nottingham within the EU Funded Marie Sklodowska-Curie Innovative Training Network "ASPIRE". ASPIRE stands for “Angular Studies of Photoelectron in Innovative Research Environments". The network consists of 11 member institutions focus on the measurement of Molecular Frame Photoelectron Angular Distributions (MFPADs), to achieve electron diffraction patterns and enable the electronic structure and dynamics of molecules to be interrogated. The attempt made here is to provide the background for the work on "Velocity Map Imaging (VMI)" technique, mostly for detecting electrons, Photoelectrons in particular as required by the aforementioned project, also the specifications of a detector in production capable of solving some of the limitations in conducting these kinds of experiments.

[1] B. J. Whitaker, Imaging in molecular dynamics: technology and applications: (a user's guide), Cambridge: Cambridge University Press, 2003. [2] J. Milnes, T. M. Conneely, The TORCH PMT: A close packing, long life MCPPMT for Cherenkov applications with a novel high granularity multi-anode, TIPP Conference 2017, Beijing, China (May 2017). [3] S. A. Leach, J. S. Lapington, J. Milnes, T. M. Conneely, R. Bugalho, S. Tavernier. Evaluation of TOFPET ASIC Performance with Microchannel Plate Photomultipliers, NDIP conference 2017, Tours, France (June 2017).

Contributed Talk

Electron-induced dissociation dynamics of small molecules found in the interstellar medium

D. Heathcote,1,* H. Köckert,1 J.W.L. Lee,1 J.A. Lomas,1 V. Richardson,1 and C. Vallance1

1 University of Oxford, Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom * [email protected]

Electron ionisation is a fundamental process in chemistry which occurs in a wide variety of systems, such as the interstellar medium, the atmosphere, and industrial processes, and has also been used extensively as an ionisation method in mass spectrometry over the past few decades. Whilst branching ratios for the formation of different fragment ions are known from mass spectrometry experiments, and many studies have been carried out using very low energy electrons, there are somewhat limited data on the fate of molecules after interacting with an ionising electron in the energy range of a few tens to hundreds of electron volts.

In our experiments, we use an electron-molecule crossed beam arrangement coupled with velocity- map imaging to study the fragmentation dynamics induced by electron ionisation [1-2]. Ions of different mass take different amounts of time to arrive at the detector, allowing them to be identified by their mass-to-charge ratio, and ions of the same mass and initial velocity map to the same position on the detector, allowing their velocity distributions to be measured. By utilising a multi- mass imaging camera such as the Pixel Imaging Mass Spectrometry (PImMS) camera, we can obtain velocity-map ion images of the scattering distribution for each of the ionic fragments in a single experimental cycle.

A further benefit of utilising a multi-mass imaging camera is that, as we record all ion hits in each experimental cycle, we can look for correlations between different ions. Covariance is a powerful statistical technique which can be used to find correlations between two variables. In our analysis we use recoil-frame covariance [3], which can be used to determine the relative velocity of an ion of interest with respect to a reference ion, allowing us to probe any channels involving multiple ionisation and subsequent dissociation in much greater detail, and revealing dynamics that typically require a coincidence imaging setup to observe.

Here, we present recently obtained results for a few small molecules found in the interstellar medium and compare the dissociation dynamics they display.

[1] H. Köckert, D. Heathcote, J.W.L. Lee, W. Zhou, V. Richardson, C. Vallance, Phys. Chem. Chem. Phys, 21 14296-14305 (2019) [2] J.N. Bull, J.W.L. Lee, C. Vallance, Phys. Rev. A, 96 042704 (2017) [3] C.S.Slater, S. Blake, M. Brouard, A. Lauer, et al., Phys. Rev. A, 91 053424 (2015)

Contributed Talk

Cold C60 molecules for high-resolution electronic spectroscopy

J. Toscano,1,* Q. Liang,1 P. B. Changala,1 M. L. Weichman,1 and J. Ye1

1 JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, University of Colorado, Boulder, CO 80309, USA. * [email protected]

Recently, the first high-resolution, ro-vibrational spectrum of the 60-atom fullerene molecule has been obtained [1]. Such experimental effort has required gas-phase C60 molecules from a hot oven to be cooled down to around 150 K within a buffer gas cell.

Here, we present the design of a new source for the generation of even colder C60 which is currently being built with the view to explore in detail the electronic spectroscopy of this highly-symmetric molecule.

[1] P. B. Changala, M. L. Weichman, K. F. Lee, M. E. Fermann and J. Ye, Science, 363, 49 (2019).

Invited Talk

Seeing the Colors in Black: Probing Distinct Chromophores in the Biopolymer Eumelanin

Bern Kohler1

1 Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH 43210 USA

The black pigment eumelanin colors human skin and is found in organisms throughout the tree of life. In addition to its natural sunscreening properties, eumelanin is attractive for photocatalysis and light harvesting due to its extremely broad absorption spectrum and the ability to manipulate its redox state with light. Eumelanin is thought to consist of a heterogeneous collection of chromophores that absorb from the UV to the near infrared, but the nature of these chromophores and their excited state decay pathways are highly uncertain because the microscopic structure of eumelanin is unknown despite decades of study. Using tunable femtosecond laser pulses to selectively excite subensembles of chromophores, broadband transient absorption experiments on a synthetic eumelanin polymer reveal transient spectral holes 0.6 eV wide that track the excitation wavelength. Hole burning proves that absorption by eumelanin is due to chemically heterogeneous chromophores, and the observed bleach recovery dynamics provide insights into interchromophore couplings. The results rule out energy migration and point instead to the ultrafast formation of charge transfer excitons. Raman spectra and TEM images disclose deep parallels between eumelanin and disordered carbon nanomaterials such as graphene oxide, graphitic carbon nitrides, and carbon dots. It is proposed that common noncovalent motifs and interactions among the chemically diverse chromophores found in this superfamily of carbonaceous materials give rise to their distinctive and nearly universal response to photoexcitation.

Invited Talk

Photoinduced Symmetry-Breaking Charge Transfer

Eric Vauthey1,*

1 Department of Physical Chemistry, 30 quai Ernest-Ansermet, 1211 Geneva, Switzerland * [email protected]

A significant number of multichromophoric systems and multipolar conjugated molecules undergo photoinduced charge transfer along one among several energetically equivalent pathways, resulting in a breaking of their symmetry.[1] Understanding and harnessing these processes is crucial for developments and applications in various areas including solar energy conversion and molecular electronics. Several of our efforts towards such a comprehension of the origins and dynamics of these symmetry-breaking phenomena will be presented.

Photoinduced charge separation between two identical sub-units will be illustrated by studies on perylene-based bichromophoric molecules.[2] They reveal the importance of the environment for the direction of the charge separation and of the coupling of the sub-units for the extent of asymmetry in charge distribution.

Excited-state symmetry breaking in quadrupolar and octupolar D-(π-A)2,3 or A-(π-D)2,3 molecules leads to a dipolar character of their electronic excited state.[3] We will show how this process can be directly visualised using time-resolved IR spectroscopy.[4] The influence of various parameters, such as solute-solvent interactions and structural disorder, on the symmetry breaking will be discussed.[5,6]

[1] E. Vauthey, ChemPhysChem, 13, 2001-2011 (2012) [2] A. Aster, et al., Chem. Sci., 10, 10629-10639 (2019) [3] F. Terenziani, et al., J. Am. Chem. Soc., 128, 15742-15755 (2006) [4] B. Dereka, et al., J. Am. Chem. Soc., 138, 4643-4649 (2016) [5] B. Dereka and E. Vauthey, J. Phys. Chem. Lett., 8, 3927-3932 (2017) [6] M. Soederberg, et al., J. Phys. Chem. Lett., 10, 2944-2948 (2019)

Contributed Talk

The photophysics of Pt(II) trans acetylide complexes for photoinduced charge separation

Julia Weinstein,1 Dimitri Chekulaev,1 Anthony Meijer,1 Theo Kane,1 Paul Scattergood,2 Mike Towrie,3 Igor Sazanovich3 and Alex Auty1*

1 Department of Chemistry, University of Sheffield, UK 2 Department of Chemistry, University of Huddersfield, UK 3 Lasers for Science Facility, RAL, Harwell, STFC, UK * [email protected]

Photoinduced charge separation (CS) is a key photophysical process underpinning light harvesting and photocatalysis.[1] This process has been studied using Transient Absorption and Time- Resolved Infrared in a Pt(II), Donor-Bridge-Acceptor, complex, bearing a Phenothiazine (PTZ) donor and a Napthaline Diimdide (NDI) acceptor (see figure 1). This builds on previous work performed in the Weinstein group, where an analogous Pt(II) complex (the monoimide) was shown to exhibit ‘controllable’ CS.[2] This involved using an IR pump to selectively excite the acetylide bonds and in doing so, completely ‘switch off’ charge separation (see figure 2).[3]

Figure 1. NDI-CC-Pt-CC-Ph-PTZ, with Figure 2. A scheme showing the excited state dynamics photoinduced charge separation shown. and IR control of the monoimide analogue.

The diimde is a stronger electron acceptor than the monoimde, thus CS is expected to be dramatically affected. I present the most recent findings on the excited state dynamics of this new Pt(II) complex, and assess the possibility of controllable electron transfer being exhibited by this system, along with the latest T-2DIR experiments which measure this effect.

[1] N. S. Lewis, Proc. Natl. Acad. Sci. U. S. A., 103, 15729–35 (2006) [2] M. Delor, et al., Science, 346, 1492–1495 (2014) [3] M. Delor, et al., Nat. Chem., 7, 689–695 (2015)

Contributed Talk

Exploring solvent and structural modification effects on the photophysics of photoredox catalysts using ultrafast transient absorption spectroscopy

M. Sneha,1,* L. Lewis-Borrell,1 A. Bhattacherjee, I. P. Clark2 and A. J. Orr-Ewing1

1 School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1LP, UK 2 Central Laser Facility, STFC, Rutherford Appleton laboratory, Didcot, Oxfordshire, OX11 0QX, UK * [email protected]

In the past decade, photoredox catalysis has emerged as a champion among the synthetic organic chemists given its ability to transform synthetic methodologies. Alongside the interest to explore its application in performing different types of chemistries (e.g., C-C, C-H couplings, radical polymerizations etc) [1], a recent drive has also been to develop new organic photocatalysts to circumvent the problems of toxicity and metal scarcity posed by the traditionally used transition metal catalysts. With new synthetic methodologies emerging every day, mechanistic studies have become more than necessary to inform rational design of these photocatalysts [2].

Using ultrafast transient vibrational and electronic absorption spectroscopies, we have studied a variety of these photocatalytic cycles used by synthetic chemists to perform different types of chemistries with the goal of developing a clear mechanistic and kinetic understanding of these reactions [3, 4].This talk will focus on the photophysical properties of phenhydrazine and phenoxazine based catalysts [5] used in these reactions and how these properties are altered by changing solvent polarities, or through structural modifications (such as adding electron withdrawing or donating groups etc) of the catalysts. Using transient absorption spectroscopy, of interest is the observation that changing these parameters influence not only the steady state properties, such as absorbance or fluorescence, but also the lifetime and character of excited singlet states (locally excited vs charge transfer) as well as intersystem crossing efficiencies. These studies offer new insights about the structure-function-dynamic relationship of these photocatalysts.

[1] N. A. Romero and D. A. Nicewicz, Chem. Rev. 116, 10075 (2016) [2] A. J. Orr-Ewing, Str. Dyn. 6, 010901 (2019) [3] D. Koyama, H. Dale, A. J. Orr-Ewing, JACS 140, 1285 (2018) [4] A. Bhattacherjee, M. Sneha, L. Lewis-Borrell, O. Tau, I. P. Clark, A.J. Orr-Ewing, Nat Comm. 10, 5152 (2019) [5] J. C. Theriot, C-H Lim, H. Yang, M. D. Ryan, C. B. Musgrave, G. M. Miyake Science 352, 1082 (2016)

Contributed Talk

An ultrafast shakedown reveals the energy landscape, relaxation dynamics and concentration of N3V:H defects in diamond

D. J. L. Coxon,1,2,3,* M. Staniforth,1,2 B. G. Breeze,1 S. E. Greenough,2 J. P. Goss,4 M. Monti,1 J. Lloyd-Hughes,1 V. G. Stavros2 and M. E. Newton1

1 Department of Physics, University of Warwick, Coventry, UK, CV4 7AL 2 Department of Chemistry, University of Warwick, Coventry, UK, CV4 7AL 3 EPSRC Centre for Doctoral Training in Diamond Science and Technology, UK 4 School of Engineering, Newcastle University, Newcastle upon Tyne, UK, NE1 7RU * [email protected]

Hydrogen-containing defects in diamond alter crystal growth processes and impact potential applications. The N3V:H defect arises from the uptake of nitrogen and hydrogen during crystal growth. It creates prominent absorption features in the infrared.[1] Transient vibrational absorption spectroscopy (TVAS) allowed us to study the “shakedown” dynamics of the N3V:H defect following pulsed (femtosecond) photoexcitation of the C–H stretch mode at 3107 cm-1. The appearance and transient decay of a ground state bleach (GSB) and two excited state absorption (ESA) features directly reveals the quantised energy levels of the C–H stretch, as well as its coupling to different vibrational modes.

Corroborating our results with a theoretical simulation of the Morse potential, we map out, for the first time, the energy relaxation pathways following infrared excitation, which include multiphonon relaxation processes and anharmonic coupling to the C–H bend mode. These studies yield crucial information into the vibrational dynamics of defects and provide unprecedented insight into their concentration and vibrational energy levels. Collectively, these new insights provide a route to quantify and probe the defects of crystalline materials.

[1] K. Iakoubovskii, G. Adriaenssens, Diam. Relat. Mater. 11, 125–131 (2002).

Invited Talk

Frequency Comb Spectroscopy for Chemical Reaction Kinetics

F. C. Roberts,1 H. J. Lewandowski,2 Billy F. Hobson,1 Julia H. Lehman1,*

1 School of Chemistry, University of Leeds, UK 2 JILA and Department of Physics, University of Colorado, USA * [email protected]

The 2005 Nobel Prize in Physics was awarded in part to John Hall and Theodor Hänsch for their development of optical frequency combs. As a simultaneously spectrally broadband and high resolution light source, frequency comb lasers have been successfully implemented in a variety of scientific fields ranging from metrology to high resolution spectroscopy. In this talk, I will highlight some recent advances in trace gas detection using infrared frequency comb laser spectroscopy, with a focus on frequency comb use in chemical reaction kinetics. I will give you an overview of frequency comb lasers, the design and implementation of a frequency comb spectrometer, and first results from our newly built system. High spectral resolution, broadband spectral coverage, and high molecular sensitivity are all achieved on an adjustable 1-50 μs timescale, making this frequency comb apparatus ideal for measuring chemical reaction kinetics where multiple infrared absorbing species can be monitored simultaneously. I will also highlight some of the critical design decisions that chemists might face should they wish to implement this advanced optical physics technology in their own laboratory.

[1] Roberts, Lewandowski, Hobson, and Lehman. Mol. Phys. 2019 (submitted)

Contributed Talk

Inverse kinetic isotope effect observed in ammonia charge exchange reactions

A. Tsikritea,1,* L.S. Petralia,1 T.P. Softley2 and B.R. Heazlewood1

1 Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, United Kingdom 2 University of Birmingham, Edgbaston, B15 2TT, United Kingdom * [email protected]

An inverse kinetic isotope effect (KIE) has been observed in ammonia charge exchange reactions with Xe+ ions. Fully deuterated ammonia molecules react more than 3 times faster in comparison to the hydrogenated molecules. We report the magnitude of the inverse KIE to be kH/kD = 0.3. Reported inverse (secondary) KIEs are rare; when they do occur, they are usually substantially weaker, with kH/kD = 0.8-0.9 [1]. Such a prominent effect cannot be explained using classical capture theory models. A proposed explanation of the phenomenon is based on the difference in the density of states of the two reaction complexes. Our observation could give an insight into the underlying mechanism behind deuterium fractionation in the interstellar medium [2].

The charge exchange reactions take place within the environment of a Ca+ Coulomb crystal, where trapped, laser-cooled Ca+ ions are used as a cold scaffold for sympathetic cooling of the reactant Xe+ ions and the product ammonia ions. The ammonia neutrals are introduced effusively into the trap area through a high-precision leak valve. Reactions are monitored by directly imaging the Ca+ laser-induced fluorescence, complemented by time-of-flight mass spectrometry detection [3].

A state-selected beam of neutral ammonia molecules produced in a Stark decelerator will be used to study the same charge exchange reactions under cold, controlled conditions. The velocity of the Stark-decelerated beam can be tuned, allowing the collision energy dependence of the charge exchange reactions to be established.

[1] M. Gomez-Gallego and M. A. Sierra, Chem. Rev., 111, 4857-4963 (2011) [2] J. L. Linsky, A. Diplas, B. E. Wood, A. Brown, T. R. Ayres and B. D. Savage, Astrophys. J., 451, 335-351 (1995) [3] K. A. E. Meyer, L. L. Pollum, L. S. Petralia, A. Tauschinsky, C. J. Rennick, T.P. Softley, B. R. Heazlewood, J. Phys. Chem. A, 119, 12449-12456 (2015)

Contributed Talk

Tracking the Ultraviolet Photochemistry of Thiophenone During and Beyond the Initial Ultrafast Ring Opening

Lea M. Ibele1,* and Basile F.E. Curchod1

1 Department of Chemistry, Durham University, Durham DH1 3LE, UK * [email protected]

In this work, we propose a complete theoretical and computational study of the photochemistry of thiophenone in gas-phase. Experimentally, the molecule was investigated using time-resolved photoelectron spectroscopy (TRPES) with a seeded extreme ultraviolet free-electron laser (FERMI). From a computational perspective, the mechanistic details of the underlying dynamics observed in the TRPES spectra, were unravelled by investigating the coupled potential energy surfaces of the lowest electronic states, both statically but also dynamically using trajectory surface hopping simulations. Important insight was obtained from theory on the ultrafast decay following photoexcitation, showing that the electronic decay to the ground state is driven by a ballistic ring- opening of thiophenone at its carbon-sulphur bond. A key feature of the TRPES experiment resides in its ability to investigate the subsequent ground-state dynamics of the vibrationally excited photoproducts. Experimentally, a very narrow distribution of binding energy was observed for the photoproducts. By continuing the decayed surface hopping trajectories with groundstate ab initio molecular dynamics, we observed the formation of at least three different different photoproducts as well as reformation of the parent thiophenone species. The distribution of binding energies computed along these dynamics agrees excellently with the measured signal and reproduces accurately its narrowness. The experimental part was carried out by a larger team of scientists with main contributions from S. Pathak, D. Rolles and M.N.R. Ashfold [1].

[1] S. Pathak, L.M. Ibele et al., submitted (2019)

Contributed Talk

Simulating Coulomb Explosion Dynamics

Lingfeng Ge,1,* Stuart W. Crane,1 and Michael N. R. Ashfold1

1 School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, UK * [email protected]

Coulomb explosion imaging (CEI) is an emerging ultrafast technique for studying photoinduced electronic and structural changes in isolated molecules. In CEI, an ultrashort, intense laser pulse removes several electrons from a neutral molecule. The resulting multiply charged cation immediately dissociates as a result of the Coulomb repulsions between the nuclei—this process is called Coulomb explosion (CE). By measuring the positions and times of arrival of the resulting fragment ions, one can determine the pre-explosion molecular structure.

However, it is no easy job to deduce the pre-explosion molecular structure from a measured image. To gain an insight into the post-explosion nuclear motions, I have simulated atomic trajectories of cis-1,2-dichloroethene (C2H2Cl2) and methyl iodide (CH3I) arising from a range of different charge states. The results clearly show two regimes: the low charge regime and the high charge regime. In the former, all the bonds do not break, and the atomic trajectories look complex; in the latter, all the bonds break, and the atomic trajectories look simple and predictable. My talk will showcase the stark differences between the two regimes.

Contributed Talk

Towards symmetry driven and nature inspired UV filter design

Emily L. Holt,1,* Michael D. Horbury,1,2 Louis M.M. Mouterde,3 Patrick Balaguer,4 Juan Cebrián,5 Laurent Blasco,5 Florent Allais3 and Vasilios G. Stavros2

1 Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK. 2 School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK. 3 URD Agro-Biotechnologies Industrielles (ABI), CEBB, AgroParisTech, 51110 Pomacle, France. 4 IRCM, Inserm, Univ. Montpellier, ICM, Montpellier, France. 5 Lubrizol Advanced Materials, C/Isaac Peral 17-Pol. Industrial Cami Ral, 08850 Gava, Spain. * E-mail: [email protected]

Sinapate esters have been identified as promising nature-based UV filters for inclusion in sunscreen formulations, as they fulfil the same photoprotective role in the leaves of plants and exhibit exemplary photostability properties [1,2]. These properties of sinapates and related cinnamates have been attributed to a reversible cis-trans photoisomerization that occurs upon UV exposure [2]. This study [3] focuses upon a sinapate ester, named diethyl sinapate (DES), which has been “symmetrically” functionalised, such that the cis and trans isomers are equivalent. Such functionalisation may alleviate safety concerns associated with current UV filters such as cinnamates, whereby the cis isomer has been identified as genotoxic [4]. This functionalisation also spectrally red-shifts the peak absorption of sinapate ester analogues into the UVA (320 – 400 nm) region, where options for adequate photoprotection are currently lacking [5].

Ultrafast transient (UV-visible) electronic absorption spectroscopy (TEAS) has been used to study the photoprotection mechanism of DES in a range of solvents, and for the first time, in a commercially available emollient, to more closely model a real-life environment. TEAS measurements of DES have also been performed on a synthetic skin mimic (VITRO-CORNEUM®, denoted VC). The returned results showed subtle differences in the photodynamical behaviours of DES across the various solvent environments, which are compared to the dynamics of DES on VC. These results highlight the importance of modelling close-to real-life conditions using fundamental spectroscopic techniques which, alongside favourable results from long-term photostability studies, endocrine disruption assays and antioxidant potential measurements, demonstrate the potential of DES to become a UVA filter of the future.

[1] J.C. Dean, R. Kusaka, P.S. Walsh, F. Allais, T.S. Zwier, J. Am. Chem. Soc. 136(42), 14780 (2014) [2] M.D. Horbury, A.L. Fluorat, S.E. Greenough, F. Allais, V.G. Stavros, Chem. Commun. 54, 936 (2018) [3] M.D. Horbury, E.L. Holt, L.M.M. Mouterde, P. Balaguer, L. Blasco, J. Cebrian, F. Allais, V.G. Stavros, Nat. Commun., 10, 4748 (2019) [4] A. Sharma, K. Banyiova, P. Babica, N. El Yamani, A.R. Collins, P. Cupr, Sci. Total Environ. 593, 18 (2017) [5] E.L.Holt, V.G. Stavros, Int. Rev. Phys. Chem., 38(2), 243 (2019)

Contributed Talk

A Conformational Study of the Alicyclic Musks Romandolide and Helvetolideby Broadband Rotational Spectroscopy

Ecaterina Burevschi,1 M. Eugenia Sanz1

1 Department of Chemistry, King’s College London, 7 Trinity Street, SE1 1DB London, UK * [email protected]

Musk odorants are important notes in perfumery for their natural, animalistic and warm scent. Structurally, musks are very diverse and it still remains unknown how their structures relate to the musky odor. In order to design new classes of musks, with scalable synthesis and higher biodegradability, it is important to understand the structural features responsible for their distinct scent. However, musks are generally very flexible and difficult to crystallise, and there is no knowledge of their structures or conformations. Here we present the conformational study of two widely used alicyclic musks, romandolide (C15H26O4) and helvetolide (C17H32O3), using chirped- pulse Fourier Transform microwave (CP-FTMW) spectroscopy in combination with theoretical methods. Seven conformations of romandolide and eight conformations of helvetolide have been identified in their respective broadband spectra. The observed conformers adopt horseshoe shapes and are stabilized by dispersion interactions between the side chain and the cyclohexane ring.

Contributed Talk

Deceleration and electrostatic trapping of cold Rydberg NO molecules

M. H. Rayment,1,* A. Deller,1 S. D. Hogan1

1 University College London, Gower Street, London, WC1E 6BT, United Kingdom * [email protected]

The large static electric dipole moments of high Rydberg states of atoms and molecules allow forces to be exerted on them using inhomogeneous electric fields [1]. This has led to the development of guides, beamsplitters, interferometers, decelerators and traps for samples in these states. These have been used, for example, to study slow decay processes of long-lived Rydberg states of H2 [2,3] and investigate ion-molecule reactions at temperatures as low as 300 mK in collisions of

Rydberg H2 molecules with ground-state H2 [4]. In this talk I will describe experiments in which we have prepared long-lived Rydberg states of NO, decelerated these molecules while they were confined in the travelling electric traps of a chip-based Rydberg-Stark decelerator [5], and studied the decay of the trapped molecules on timescales up to 1 ms.

[1] S. D. Hogan, "Rydberg-Stark deceleration of atoms and molecules", EPJ Techniques and Instrumentation 3, 1 (2016) [2] S. D. Hogan, Ch. Seiler and F. Merkt, "Rydberg-state-enabled deceleration and trapping of cold molecules", Phys. Rev. Lett. 103, 123001 (2009) [3] Ch. Seiler, Ph.D. Thesis, ETH Zürich (2013) [4] P. Allmendinger, J. Deiglmayr, K. Höveler, O. Schullian and F. Merkt, "Observation of + + enhanced rate coefficients in the H2 + H2 -> H3 + H reaction at low collision energies", J. Chem. Phys. 145, 244316 (2016) [5] P. Lancuba and S. D. Hogan, "Transmission-line decelerators for atoms in high Rydberg states", Phys. Rev. A 90, 053420 (2014)

Contributed Talk

Liquid-phase MeV Ultrafast Electron Diffraction

J. P. F. Nunes1*, K. Ledbetter2,3, M. Lin4, M. Kozina4, D. DePonte4, E. Biasin3, M. Centurion1, M. Dunning4, S. Guillet4, K. Jobe4, Y. Liu5, M. Mo3, X. Shen4, B. Sublett4, S. Weathersby4, C. Yoneda4, T. J. A. Wolf3, J. Yang4, A. A. Cordones3, and X. J. Wang4

1 University of Nebraska-Lincoln, Lincoln, USA 2 Stanford University, Stanford, USA 3 Stanford PULSE Institute, Menlo Park, USA 4 SLAC National Accelerator Laboratory, Menlo Park, USA 5 Stony Brook University, Stony Brook, USA * [email protected]

The conversion of light into usable chemical and mechanical energy mediates many important processes in nature, e.g. vision, plant photosynthesis and DNA photodamage. To understand the structure-function relationships regulating these processes one must strive to study them in their natural environment, i.e. in solution. This talk focuses on the design of an Ultrafast Electron Diffraction (UED) instrument specifically developed for the study of photochemical reactions in liquids. This instrument combines the electron beam properties of the SLAC MeV UED facility [1] with ultrathin liquid-sheet jet technology [2] to overcome limitations associated with the shallow penetration depth of electron and information loss due to multiple scattering. The capabilities of liquid-phase MeV UED are showcased in the study of liquid water, where its structure was resolved up to the 3rd hydration shell with a spatial resolution of 0.6 Å; and where preliminary time-resolved experiments demonstrated a temporal resolution of 200 fs. This work demonstrates the potential of liquid-phase MeV UED as an alternative and/or complementary tool to time-resolved X-ray scattering techniques currently employed in the study of solution-phase photochemistry.

Figure: CAD model of the liquid-phase MeV UED beamline at SLAC.

References: [1] Weathersby et al, Rev. Sci. Instrum., 86, 073702 (2015). [2] Koralek et al, Nature Communications, 9, 1–8 (2018)

Contributed Talk

Probing the Reactivity of Gold Clusters using IR Action Spectroscopy

A. E. Green,1,* G. Meizyte,1 R. H. Brown,1 S. Schaller,2 W. Schöllkopf,2 A. S. Gentleman,1 A. Fielicke2 and S. R. Mackenzie1

1 Physical and Theoretical Chemistry Laboratory, University of Oxford, United Kingdom 2 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany * [email protected]

Using infrared free electron laser photodissociation spectroscopy, we can investigate details of potential energy surfaces for a range of important catalytic reactions. In particular, the molecular vibrations allow us to explore the extent of molecular activation upon interaction with an isolated metal cluster, and consequently identify some key features to aim for in catalytic processes.[1]

+ In this way, infrared studies of carbonyl sulfide adsorbed to gas phase cationic gold clusters, Aun (n=2-10), not only probe the structure and degree of OCS activation, but present evidence of the infrared light itself driving chemistry on cluster surfaces. Infrared induced chemistry has previously been studied with N2O on rhodium clusters,[2] but now we develop this even further, as the reactivity is highly dependent on the size of the cluster.

+ + + Au10 -(OCS), along with studies of Au10 -(N2O) and even Au10 -Ar, present a consistent broad infrared absorption, unassignable to cluster vibrations. We postulate this feature is a result of very + low lying electronic structure of the core Au10 cluster.

[1] A. E. Green, J. Justin, W. Schöllkopf, A. S. Gentleman, A. Fielicke and S. R. Mackenzie, Angew. Chem. Int. Ed., 57 14822 (2018) [2] S. M. Hamilton, W. S. Hopkins, D. J. Harding, T. R. Walsh, P. Gruene, M. Haertelt, A. Fielicke, G. Meijer, S. Mackenzie, J. Am. Chem. Soc

List of Posters

University of Warwick 6th – 8th January 2020

List of Posters

# Presenter’s name Poster title

Real-space imaging of OD and OH 1 Adam G. Knight collisions with liquid surfaces

Alanah Grant-St Mass spectrometric analysis of citrus fruits 2 James using machine learning methods

Synthesis of Mycosporine-like Amino Acid 3 Adam M. Cowden Derivatives (MAADs) for sunscreen applications

Ultrafast spectroscopy of Mycosporine-like 4 Abbie Whittock Amino Acid Derivatives (MAADs) for sunscreen applications

5 Alexander R. Davies Duschinsky mixing in meta-fluorotoluene

Molecular activation and reactivity on small 6 Alice Green metal clusters

Molecular dynamics simulations of 7 Aisiling Stewart interfaces: the oleic acid family

Generation of a universal probe for time resolved photoelectron spectroscopy: High 8 Briony Downes-Ward Harmonic generation in a semi-infinite gas cell

Spectral imaging of thrombus for prognostic 9 Charlotte Greenhalgh evaluation of STEMI patients

Ultrafast dynamics of photo-oxidation of the 10 Caleb Jordan photoactive yellow protein chromophores in the condensed phase

Studies of ion-radical reaction dynamics by 11 Chloe Miossec combining a Zeeman decelerator and a cryogenic ion-trap

Control and measurement of cold ammonia 12 Paul Bertier orientation

Photoelectron velocity map imaging of 13 Christopher W. West charged aerosol droplets

Whodunnit? Towards solving the puzzle of 14 Daniel J. L. Coxon the 3237 cm-1 feature in diamond

Photodissociation and velocity-map imaging 15 Divya Popat of N,N-Dimethylformamide at 193 nm

Resonance enhanced multiphoton photo- 16 Dhirendra P. Singh electron circular dichroism (REMPI- PECD) of monoterpenes

Dissociation behaviour of CO as a Ligand 17 Edward Brewer + on bimetallic (NbxRhy)n clusters

Studies into the effects of hydrogen 18 Edward Plackett bonding on excited state dynamics

Absolute density measurements of trace 19 Eckart Wrede amounts of OH radicals

Frequency comb spectroscopy for reaction 20 Frances C. Roberts kinetics

The interaction of cation dyes with gold 21 Fengyuan Shan nanoparticles and nanoclusters

Adsorption of nitrous oxide on platinum, 22 Gabriele Meizyte gold, and cobalt cationic clusters

Studying the electron transfer driven 23 Georgia Thornton polymerisation of N-ethylcarbazole using transient absorption spectroscopy

MCTDH on-the-fly: Efficient grid-based 24 Gareth W. Richings quantum dynamics without pre-computed potential energy surfaces

A spectroscopic and theoretical 25 Haleema Otaif investigation of color tuning in luminescent iridium (III) complexes

Velocity map imaging of electron ionisation 26 James Lomas of small molecules

Towards molecular frame photoelectron angular distributions from simple polyatomic 27 James O.F. Thompson systems: application to electronically excited aniline

Johanna Rademacher Electronic spectroscopy of endohedral 28 and Elliott Reedy fullerene cations

Positional substitution effects on a 29 Jack M. Woolley photoisomerisation pathway

Illuminating the ultrafast dynamics of 30 Joseph J. Broughton thiophene

IR spectroscopy of acetic acid dimers in 31 Julia Davies helium nanodroplets

A “bottom-up” approach in ultrafast 32 Konstantina Krokidi dynamics of methyl cinnamate

Mid-Infrared frequency modulated 33 Katya Moncrieff spectroscopy as a probe of scattering dynamics at the gas-liquid interface

The efficient calculation of ACCSA rate 34 Kibum Park constants for ion-molecule reactions at cold temperatures

Photoexcitation of iodide ion-thiouracil 35 Kelechi .O. Uleanya clusters: Probing electron capture by non- native nucleobase

A theoretical study of the reaction between 36 Lok Hin Desmond Li the CN radical and CH2O

A change of scene: atom-diatom scattering 37 Matthew L. Costen in an electronically excited state

A surface-adsorbed comparison of 38 Martin Lea established and emerging molecular switch architectures

IR spectroscopy of propargyl alcohol dimers 39 Martin Mugglestone in helium nanodroplets

Absolute fluorescence quantum yield of 40 Hendrik Nahler acetone

BoostCrop: Ultrafast time-resolved insights 41 Nat d. N. Rodrigues into light-to-heat mechanisms for crop growth

Fusing gas-phase laser action spectroscopy with solution-phase photolysis 42 Natalie G. K. Wong systems to explore the photochemistry of sunscreens

Ultrafast molecular spectroscopy using a 43 Nikoleta Kotsina hollow-core photonic crystal fiber light source

Low temperature gas phase reaction rate coefficient measurements: Toward 44 Niclas West modelling of stellar winds and the interstellar medium

Time-resolved liquid-microjet photoelectron 45 Omri Tau spectroscopy of phenol

Exploring the excited state character of 9- 46 Patrick Kimber (4-nitroaryl)carbazole derivatives using wavefunction analysis

Patrick Murton and Measuring magnetic field effects in 47 Jessica Flemming proteins

Scattering dynamics at the gas-liquid 48 Paul D. Lane interfaces

Liquid-microjet photoelectron spectroscopy 49 River Riley of the green fluorescent protein chromophore

Photoelectron spectroscopy of hot carrier 50 Rosin Tapley decay in plasmonic nanostructures

Investigation of the photogenerated states and phototransformation kinetics of 51 Seham Alzamanan transition metals complexes using electron paramagnetic resonance (EPR) spectroscopy

A novel approach in the steady-state 52 Sofia Goia and ultrafast photodynamics study of redox-active species

Studying gas-liquid surface reactions using 53 Stuart J. Greaves velocity map imaging

Simulating absorption spectra in Maliamide: 55 Sandra Gomez do we need excited state dynamics?

Coulomb explosion imaging: A tool for 56 Stuart W. Crane molecular structure determination

Understanding the photodynamics of plant 57 Temitope T. Abiola UV filter derivatives as commercial sunscreens

Exploring the photophysics of 6-amino-5- 58 William A. Whitaker nitro-2(1H)-pyridone, a “non-natural DNA” Building Block

Unravelling the redox properties of 59 William G. Fortune phenolates using photoelectron spectroscopy