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Two-body dissociation of isoxazole following double photoionization - an experimental PEPIPICO and theoretical DFT and MP2 study.
Wasowicz, Tomasz J; Dabkowska, Iwona; Kivimäki, Antti; Richter, Robert.
Afiliação
  • Wasowicz TJ; Division of Complex Systems Spectroscopy, Institute of Physics and Computer Science, Gdansk University of Technology, ul. G. Narutowicza 11/12, 80-233 Gdansk, Poland. tomasz.wasowicz1@pg.edu.pl.
  • Dabkowska I; Department of Analytical Chemistry, Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-308 Gdansk, Poland.
  • Kivimäki A; MAX IV Laboratory, Lund University, 22100 Lund, Sweden.
  • Richter R; Elettra-Sincrotrone Trieste, 34149 Trieste, Italy.
Phys Chem Chem Phys ; 25(46): 31655-31666, 2023 Nov 29.
Article em En | MEDLINE | ID: mdl-37964643
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.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Phys Chem Chem Phys Assunto da revista: BIOFISICA / QUIMICA Ano de publicação: 2023 Tipo de documento: Article País de afiliação: Polônia País de publicação: Reino Unido

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Phys Chem Chem Phys Assunto da revista: BIOFISICA / QUIMICA Ano de publicação: 2023 Tipo de documento: Article País de afiliação: Polônia País de publicação: Reino Unido