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Two-body dissociation of isoxazole following double photoionization - an experimental PEPIPICO and theoretical DFT and MP2 study

Wasowicz, Tomasz J. ; Dąbkowska, Iwona ; Kivimäki, Antti LU and Richter, Robert (2023) In Physical Chemistry Chemical Physics 25(46). p.31655-31666
Abstract

The dissociative double photoionization of isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5-36 eV photon energy range using vacuum ultraviolet (VUV) synchrotron radiation excitation combined with ion time-of-flight (TOF) spectrometry and photoelectron-photoion-photoion coincidence (PEPIPICO) technique. Five well-resolved two-body dissociation channels have been identified in the isoxazole's coincidence maps, and their appearance energies have been determined. The coincidence yield curves of these dissociation channels have been obtained in the photon energy ranges from their appearance energies up to 36 eV. The double photoionization of isoxazole produces a... (More)

The dissociative double photoionization of isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5-36 eV photon energy range using vacuum ultraviolet (VUV) synchrotron radiation excitation combined with ion time-of-flight (TOF) spectrometry and photoelectron-photoion-photoion coincidence (PEPIPICO) technique. Five well-resolved two-body dissociation channels have been identified in the isoxazole's coincidence maps, and their appearance energies have been determined. The coincidence yield curves of these dissociation channels have been obtained in the photon energy ranges from their appearance energies up to 36 eV. The double photoionization of isoxazole produces a C3H3NO2+ transient dication, which decomposes into fragments differing from previously reported photofragmentation products of isoxazole. We have found no evidence of pathways leading to the C3H2NO+, HCN+, C2H2O+, C3HN+, or C2H2+ fragments or their neutral counterparts that have been observed in previous neutral photodissociation and single photoionization studies. Instead, the dissociation of isoxazole after the ejection of two electrons is bond-selective and is governed by two reactions, HCO+ + H2CCN+ and H2CO+ + HCCN+, whose appearance energies are 28.6 (±0.3) and 29.4 (±0.3) eV, respectively. A third dissociation channel turns out to be a variant of the most intense channel (HCO+ + H2CCN+), where one of the fragment ions contains a heavy isotope. Two minor dissociation channels occurring at higher energies, CO+ + CH3CN+ and CN+ + H3CCO+, are also identified. The density functional and ab initio quantum chemical calculations have been performed to elucidate the dissociative charge-separating mechanisms and determine the energies of the observed photoproducts. The present work unravels hitherto unexplored photodissociation mechanisms of isoxazole and thus provides deeper insight into the photophysics of five-membered heterocyclic molecules containing two heteroatoms.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
25
issue
46
pages
12 pages
publisher
Royal Society of Chemistry
external identifiers
  • pmid:37964643
  • scopus:85176814637
ISSN
1463-9076
DOI
10.1039/d3cp03760f
language
English
LU publication?
yes
id
b13d701f-e5f4-4d00-b39f-1035f30a7ac9
date added to LUP
2024-01-11 10:59:14
date last changed
2024-04-26 06:45:19
@article{b13d701f-e5f4-4d00-b39f-1035f30a7ac9,
  abstract     = {{<p>The dissociative double photoionization of isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5-36 eV photon energy range using vacuum ultraviolet (VUV) synchrotron radiation excitation combined with ion time-of-flight (TOF) spectrometry and photoelectron-photoion-photoion coincidence (PEPIPICO) technique. Five well-resolved two-body dissociation channels have been identified in the isoxazole's coincidence maps, and their appearance energies have been determined. The coincidence yield curves of these dissociation channels have been obtained in the photon energy ranges from their appearance energies up to 36 eV. The double photoionization of isoxazole produces a C<sub>3</sub>H<sub>3</sub>NO<sup>2+</sup> transient dication, which decomposes into fragments differing from previously reported photofragmentation products of isoxazole. We have found no evidence of pathways leading to the C<sub>3</sub>H<sub>2</sub>NO<sup>+</sup>, HCN<sup>+</sup>, C<sub>2</sub>H<sub>2</sub>O<sup>+</sup>, C<sub>3</sub>HN<sup>+</sup>, or C<sub>2</sub>H<sub>2</sub><sup>+</sup> fragments or their neutral counterparts that have been observed in previous neutral photodissociation and single photoionization studies. Instead, the dissociation of isoxazole after the ejection of two electrons is bond-selective and is governed by two reactions, HCO<sup>+</sup> + H<sub>2</sub>CCN<sup>+</sup> and H<sub>2</sub>CO<sup>+</sup> + HCCN<sup>+</sup>, whose appearance energies are 28.6 (±0.3) and 29.4 (±0.3) eV, respectively. A third dissociation channel turns out to be a variant of the most intense channel (HCO<sup>+</sup> + H<sub>2</sub>CCN<sup>+</sup>), where one of the fragment ions contains a heavy isotope. Two minor dissociation channels occurring at higher energies, CO<sup>+</sup> + CH<sub>3</sub>CN<sup>+</sup> and CN<sup>+</sup> + H<sub>3</sub>CCO<sup>+</sup>, are also identified. The density functional and ab initio quantum chemical calculations have been performed to elucidate the dissociative charge-separating mechanisms and determine the energies of the observed photoproducts. The present work unravels hitherto unexplored photodissociation mechanisms of isoxazole and thus provides deeper insight into the photophysics of five-membered heterocyclic molecules containing two heteroatoms.</p>}},
  author       = {{Wasowicz, Tomasz J. and Dąbkowska, Iwona and Kivimäki, Antti and Richter, Robert}},
  issn         = {{1463-9076}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{46}},
  pages        = {{31655--31666}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Physical Chemistry Chemical Physics}},
  title        = {{Two-body dissociation of isoxazole following double photoionization - an experimental PEPIPICO and theoretical DFT and MP2 study}},
  url          = {{http://dx.doi.org/10.1039/d3cp03760f}},
  doi          = {{10.1039/d3cp03760f}},
  volume       = {{25}},
  year         = {{2023}},
}