A1 Refereed original research article in a scientific journal
Exploring the ultrafast and isomer-dependent photodissociation of iodothiophenes via site-selective ionization
Authors: Razmus Weronika O., Allum Felix, Harries James, Kumagai Yoshiaki, Nagaya Kiyonobu, Bhattacharyya Surjendu, Britton Mathew, Brouard Mark, Bucksbaum Philip H., Cheung Kieran, Crane Stuart W., Fushitani Mizuho, Gabalski Ian, Gejo Tatsuo, Ghrist Aaron, Heathcote David, Hikosaka Yasumasa, Hishikawa Akiyoshi, Hockett Paul, Jones Ellen, Kukk Edwin, Iwayama Hiroshi, Lam Huynh V. S., McManus Joseph W., Milesevic Dennis, Mikosch Jochen, Minemoto Shinichirou, Niozu Akinobu, Orr-Ewing Andrew J., Owada Shigeki, Rolles Daniel, Rudenko Artem, Townsend Dave, Ueda Kiyoshi, Unwin James, Vallance Claire, Venkatachalam Anbu, Wada Shin-ichi, Walmsley Tiffany, Warne Emily M., Woodhouse Joanne L., Burt Michael, Ashfold Michael N. R., Minns Russell S., Forbes Ruaridh
Publisher: Royal Society of Chemistry
Publication year: 2024
Journal: Physical Chemistry Chemical Physics
Journal name in source: Physical chemistry chemical physics : PCCP
Journal acronym: Phys Chem Chem Phys
Volume: 26
Issue: 16
First page : 12725
Last page: 12737
ISSN: 1463-9076
eISSN: 1463-9084
DOI: https://doi.org/10.1039/d3cp06079a(external)
Web address : https://pubs.rsc.org/en/content/articlelanding/2024/cp/d3cp06079a(external)
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/387703921(external)
C-I bond extension and fission following ultraviolet (UV, 262 nm) photoexcitation of 2- and 3-iodothiophene is studied using ultrafast time-resolved extreme ultraviolet (XUV) ionization in conjunction with velocity map ion imaging. The photoexcited molecules and eventual I atom products are probed by site-selective ionization at the I 4d edge using intense XUV pulses, which induce multiple charges initially localized to the iodine atom. At C-I separations below the critical distance for charge transfer (CT), charge can redistribute around the molecule leading to Coulomb explosion and charged fragments with high kinetic energy. At greater C-I separations, beyond the critical distance, CT is no longer possible and the measured kinetic energies of the charged iodine atoms report on the neutral dissociation process. The time and momentum resolved measurements allow determination of the timescales and the respective product momentum and kinetic energy distributions for both isomers, which are interpreted in terms of rival 'direct' and 'indirect' dissociation pathways. The measurements are compared with a classical over the barrier model, which reveals that the onset of the indirect dissociation process is delayed by ∼1 ps relative to the direct process. The kinetics of the two processes show no discernible difference between the two parent isomers, but the branching between the direct and indirect dissociation channels and the respective product momentum distributions show isomer dependencies. The greater relative yield of indirect dissociation products from 262 nm photolysis of 3-iodothiophene (cf. 2-iodothiophene) is attributed to the different partial cross-sections for (ring-centred) π∗ ← π and (C-I bond localized) σ∗ ← (n/π) excitation in the respective parent isomers.
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