Time-resolved momentum imaging of UV photodynamics in structural isomers of iodopropane probed by site-selective XUV ionization

Felix Allum; Yoshiaki Kumagai; Kiyonobu Nagaya; James R. Harries; Hiroshi Iwayama; Mathew Britton; Philip H. Bucksbaum; Michael Burt; Mark Brouard; Briony Downes-Ward; Taran Driver; David Heathcote; Paul Hockett; Andrew J. Howard; Jason W. L. Lee; Yusong Liu; Edwin Kukk; Joseph W. McManus; Dennis Milešević; Russell S. Minns; Akinobu Niozu; Johannes Niskanen; Andrew J. Orr-Ewing; Shigeki Owada; Patrick Robertson; Daniel Rolles; Artem Rudenko; Kiyoshi Ueda; James Unwin; Claire Vallance; Tiffany Walmsley; Michael N. R. Ashfold; Ruaridh Forbes

doi:10.1039/D5CP02929E

Time-resolved momentum imaging of UV photodynamics in structural isomers of iodopropane probed by site-selective XUV ionization

Felix Allum,

*^abc Yoshiaki Kumagai,

^de Kiyonobu Nagaya,^f James R. Harries,^g Hiroshi Iwayama,^hi Mathew Britton,^c Philip H. Bucksbaum,^b Michael Burt,^jk Mark Brouard,

^j Briony Downes-Ward,

^l Taran Driver,

^c David Heathcote,

^j Paul Hockett,

^m Andrew J. Howard,^b Jason W. L. Lee,

^a Yusong Liu,^b Edwin Kukk,ⁿ Joseph W. McManus,^j Dennis Milešević,

^j Russell S. Minns,

^l Akinobu Niozu,

^o Johannes Niskanen,

ⁿ Andrew J. Orr-Ewing,

^p Shigeki Owada,^qr Patrick Robertson,^js Daniel Rolles,

^t Artem Rudenko,^t Kiyoshi Ueda,^u James Unwin,^j Claire Vallance,

^j Tiffany Walmsley,

^j Michael N. R. Ashfold

^p and Ruaridh Forbes

*^cv

Author affiliations

* Corresponding authors

^a Deutsches Elektronen-Synchrotron DESY, Notkestraße85, 22607 Hamburg, Germany
E-mail: felix.allum@desy.de

^b Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA

^c Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA

^d Department of Applied Physics, Tokyo University of Agriculture and Technology, Tokyo, Japan

^e Department of Physics, Nara Women's University, Nara 630-8506, Japan

^f Department of Physics, Kyoto University, Kyoto 606-8502, Japan

^g QST, SPring-8, Kouto 1-1-1, Sayo, Hyogo, Japan

^h Institute for Molecular Science, Okazaki 444-8585, Japan

ⁱ Sokendai (The Graduate University for Advanced Studies), Okazaki 444-8585, Japan

^j Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, UK

^k Department of Chemistry, Trent University, Peterborough, ON K9L 0G2, Canada

^l School of Chemistry and Chemical Engineering, University of Southampton, Southampton, UK

^m National Research Council of Canada, 100 Sussex Dr Ottawa, ON K1A 0R6, Canada

ⁿ Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland

^o Graduate School of Humanities and Social Sciences, Hiroshima University, Higashi-Hiroshima, Japan

^p School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK

^q RIKEN SPring-8 Center, Sayo, Hyogo, Japan

^r Japan Synchrotron Radiation Research Institute, Hyogo, Japan

^s School of Chemistry, University of Nottingham, Nottingham, UK

^t J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA

^u Department of Chemistry, Tohoku University, Sendai 980-8578, Japan

^v Department of Chemistry, University of California, Davis, California 95616, USA
E-mail: ruforbes@ucdavis.edu

Abstract

The photodynamics of 1- and 2-iodopropane (1 and 2-IP) were studied in a time-resolved scheme incorporating ultraviolet (UV) excitation and extreme ultraviolet (XUV) probing, which initiates photoionization selectively from the I 4d core orbital. UV absorption in the A-band of both isomers leads to prompt C–I bond fission, with significant disposal of internal energy into the propyl radical product. Site-selective ionization enables a range of charge transfer (CT) processes between the nascent highly charged iodine ions and neutral propyl radicals, dependent on the interfragment distance at the instant of ionization. Subtle differences in the dynamics of these CT processes between the two isomers are observed. In 1-IP, the kinetic energies of iodine ions produced by UV photodissociation and subsequent XUV multiple ionization increased notably over the first few hundred femtoseconds, which could be understood in terms of differing gradients along the photodissociation coordinates of the neutral and polycationic states involved in the pump and probe steps, respectively. Led by a recent report of HI elimination in UV photoexcited 2-IP [Todt et al., Phys. Chem. Chem. Phys., 22(46), 27338 (2020)], we also model the most likely signatures of this process in the present experiment, and can identify signal in the 2-IP data (that is absent or significantly weaker in the data from the unbranched 1-IP isomer) that is consistent with such a process occurring on ultrafast timescales.

Physical Chemistry Chemical Physics

Time-resolved momentum imaging of UV photodynamics in structural isomers of iodopropane probed by site-selective XUV ionization

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Time-resolved momentum imaging of UV photodynamics in structural isomers of iodopropane probed by site-selective XUV ionization

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