A comprehensive investigation of low-energy electron attachment and electron ionization of the nimorazole radiosensitizer used in cancer radiation therapy is reported by means of a gas-phase crossed beam experiment in an electron energy range from 0 eV to 70 eV. Regarding negative ion formation, we discuss the formation of fifteen fragment anions in the electron energy range of 0 eV–10 eV, where the most intense signal is assigned to the nitrogen dioxide anion NO2−. The other fragment anions have been assigned to form predominantly from a common temporary negative ion state close to 3 eV of the nitroimidazole moiety, while the morpholine moiety seems to act only as a spectator in the dissociative electron attachment event to nimorazole. Quantum chemical calculations have been performed to help interpreting the experimental data with thermochemical thresholds, electron affinities, and geometries of some of the neutral molecules. As far as positive ion formation is concerned, the mass spectrum at the electron energy of 70 eV shows a weakly abundant parent ion and C5H10NO+ as the most abundant fragment cation. We report appearance energy (AE) measurements for six cations. For the intact nimorazole molecular cation, the AE of 8.16 ± 0.05 eV was obtained, which is near the presently calculated adiabatic ionization energy.
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21 February 2021
Research Article|
February 19 2021
Formation of negative and positive ions in the radiosensitizer nimorazole upon low-energy electron collisions
R. Meißner;
R. Meißner
1
Institute for Ion Physics and Applied Physics and Center for Biomolecular Sciences (CMBI), University of Innsbruck
, Technikerstrasse 25, A-6020 Innsbruck, Austria
2
Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa
, 2829-516 Caparica, Portugal
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L. Feketeová;
L. Feketeová
1
Institute for Ion Physics and Applied Physics and Center for Biomolecular Sciences (CMBI), University of Innsbruck
, Technikerstrasse 25, A-6020 Innsbruck, Austria
3
Institut de Physique des 2 Infinis, CNRS/IN2P3, UMR5822, Université de Lyon, Université Claude Bernard Lyon 1
, 43 Bd du 11 november 1918, 69622 Villeurbanne, France
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A. Bayer;
A. Bayer
1
Institute for Ion Physics and Applied Physics and Center for Biomolecular Sciences (CMBI), University of Innsbruck
, Technikerstrasse 25, A-6020 Innsbruck, Austria
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P. Limão-Vieira
;
P. Limão-Vieira
a)
2
Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa
, 2829-516 Caparica, Portugal
a)Authors to whom correspondence should be addressed: plimaovieira@fct.unl.pt and Stephan.Denifl@uibk.ac.at
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S. Denifl
S. Denifl
a)
1
Institute for Ion Physics and Applied Physics and Center for Biomolecular Sciences (CMBI), University of Innsbruck
, Technikerstrasse 25, A-6020 Innsbruck, Austria
a)Authors to whom correspondence should be addressed: plimaovieira@fct.unl.pt and Stephan.Denifl@uibk.ac.at
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a)Authors to whom correspondence should be addressed: plimaovieira@fct.unl.pt and Stephan.Denifl@uibk.ac.at
J. Chem. Phys. 154, 074306 (2021)
Article history
Received:
December 09 2020
Accepted:
January 25 2021
Citation
R. Meißner, L. Feketeová, A. Bayer, P. Limão-Vieira, S. Denifl; Formation of negative and positive ions in the radiosensitizer nimorazole upon low-energy electron collisions. J. Chem. Phys. 21 February 2021; 154 (7): 074306. https://doi.org/10.1063/5.0040045
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