Ultraviolet photochemistry of 2-bromothiophene explored using universal ionization detection and multi-mass velocity-map imaging with a PImMS2 sensor

Rebecca A Ingle, Christopher S Hansen, Emma Elsdon, Matthew Bain, Simon J King, Jason W L Lee, Mark Brouard, Claire Vallance, Renato Turchetta, Michael N R Ashfold

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

The ultraviolet photochemistry of 2-bromothiophene (C4H3SBr) has been studied across the wavelength range 265-245 nm using a velocity-map imaging (VMI) apparatus recently modified for multi-mass imaging and vacuum ultraviolet (VUV, 118.2 nm) universal ionization. At all wavelengths, molecular products arising from the loss of atomic bromine were found to exhibit recoil velocities and anisotropies consistent with those reported elsewhere for the Br fragment [J. Chem. Phys. 142, 224303 (2015)]. Comparison between the momentum distributions of the Br and C4H3S fragments suggest that bromine is formed primarily in its ground (2P3/2) spin-orbit state. These distributions match very well at high momentum, but relatively fewer slow moving molecular fragments were detected. This is explained by the observation of a second substantial ionic product, C3H+ 3. Analysis of ion images recorded simultaneously for several ion masses and the results of high-level ab initio calculations suggest that this fragment ion arises from dissociative ionization (by the VUV probe laser) of the most internally excited C4H3S fragments. This study provides an excellent benchmark for the recently modified VMI instrumentation and offers a powerful demonstration of the emerging field of
multi-mass VMI using event-triggered, high frame-rate sensors and universal ionization.
Original languageEnglish
Article number013914
Number of pages11
JournalJournal of Chemical Physics
Volume147
Issue number1
Early online date1 Apr 2017
DOIs
Publication statusPublished - 7 Jul 2017

Keywords

  • Photodissociation
  • Ion imaging
  • Multi-mass imaging
  • Universal ionization
  • Universal detection

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