The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract:The resonant attachment of a free electron to a closed shell neutral molecule, and the interplay between the following electron detachment and electronic relaxation channels represents a fundamental but common process throughout chemical and biochemical systems. The new methodology of anion frequency-resolved photoelectron imaging is detailed and used to map-out molecular excited state dynamics of gas-phase para-benzoquinone, which is the electron accepting moiety in many biological electron-transfer chains. Three-dimensional spectra of excitation energy, electron kinetic energy and electron ejection anisotropy reveal clear fingerprints of excited and intermediate state dynamics. The results show that many of the excited states are strongly coupled, providing a route to forming the ground state radical anion, despite the fact that the electron is formally unbound in the excited states. The relation of our method to electron impact attachment studies and the key advantages, including the extension to time-resolved dynamics and to larger molecular systems is discussed.

Frequency-, angle-, and time-resolved photoelectron imaging of gas-phase menadione (vitamin K3) radical anions is used to show that quasi-bound resonances of the anion can act as efficient doorway states to produce metastable ground electronic state anions on a sub-picosecond timescale.

The experimental determination of absolute total electron impact ionization cross-sections for polyatomic molecules has traditionally been a difficult task and restricted to a small range of species. This article reviews the performance of three models to estimate the maximum ionization cross-sections of some 65 polyatomic organic and halocarbon species. Cross-sections for all of the species studied have been measured experimentally using the same instrument, providing a complete data set for comparison with the model predictions. The three models studied are the empirical correlation between maximum ionization cross-section and molecular polarizability, the well-known binary encounter Bethe (BEB) model, and the functional group additivity model. The excellent agreement with experiment found for all three models, provided that calculated electronic structure parameters of suitably high quality are used for the first two, allows the prediction of total electron-impact ionization cross-sections to at least 7% precision for similar molecules that have not been experimentally characterized.

. (2015) 'Excited state dynamics of the isolated green uorescent protein chromophore anion following UV excitation.', Journal of physical chemistry B., 119 (10). pp. 3982-3987. Further information on publisher's website:http://dx.doi.org/10.1021/acs.jpcb.5b01432Publisher's copyright statement:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in The Journal of Physical Chemistry B, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see http://dx.doi.org/10.1021/acs.jpcb.5b01432. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

Non-valence states in neutral molecules (Rydberg states) have well-established roles and importance in photochemistry, however, considerably less is known about the role of non-valence states in photo-induced processes in anions. Here, femtosecond time-resolved photoelectron imaging is used to show that photoexcitation of the S1(ππ*) state of the methyl ester of deprotonated para-coumaric acid – a model chromophore for photoactive yellow protein (PYP) – leads to a bifurcation of the excited state wavepacket. One part remains on the S1(ππ*) state forming a twisted intermediate, whilst a second part leads to the formation of a non-valence (dipole-bound) state. Both populations eventually decay independently by vibrational autodetachment. Valence-to-non-valence internal conversion has hitherto not been observed in the intramolecular photophysics of an isolated anion, raising questions into how common such processes might be, given that many anionic chromophores have bright valence states near the detachment threshold.

Accurate ionization cross-sections for DNA and RNA constituents in the condensed or aqueous phase are important parameters for models simulating radiation damage to genetic material in living cells. In this work, absolute gas-phase electron total ionization cross-sections (TICSs) have been measured for a series of six aromatic and eight non-aromatic cyclic species that can be considered as prototype functional group analogues for the nucleobases and sugar backbone constituents of DNA and RNA. TICSs for water, hexane, and ethylacetamide (a peptide bond analogue) are also reported. The experimental apparatus utilizes a cylindrical ion collector that surrounds the ionization region, providing essentially unit detection efficiency. Two theoretical models, the polarizability-correlation method and binary-encounter Bethe theory, are able to reproduce the measured maximum TICS well for all species studied. An empirical energy-dependent correction is found to yield improvement in the agreement between experimental energy-dependent cross sections and the predictions of the BEB model. Having characterised and optimised the performance of both models, they are then used to predict TICSs for gas-phase DNA and RNA nucleobases and sugars. Direct experimental determinations of TICSs for these species are difficult because of their low volatility, which makes it difficult to prepare suitable gas-phase samples for measurement.

Donor-acceptor Stenhouse adducts (DASAs) are a new class of photoswitching molecules with excellent fatigue resistance and synthetic tunability. Here, tandem ion mobility mass spectrometry coupled with laser excitation is used to characterize the photocyclization reaction of isolated, charge-tagged DASA molecules over the 450-580 nm range. The experimental maximum response at 530 nm agrees with multireference perturbation theory calculations for the S ← S transition maximum at 533 nm. Photocyclization in the gas phase involves absorption of at least two photons; the first photon induces Z-E isomerization from the linear isomer to metastable intermediate isomers, while the second photon drives another E-Z isomerization and 4π-electrocyclization reaction. Cyclization is thermally reversible in the gas phase with collisional excitation.

Formation and mode-specific autodetachment from a dipole-bound state in a radical anion dimer is observed in the frequency and time-domains.