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Lozano AI, Kumar S, Pereira PJS, Kerkeni B, García G, Limão-Vieira P. Low-lying Negative Ion States Probed in Potassium - Ethanol Collisions. Chemphyschem 2024; 25:e202400314. [PMID: 38630012 DOI: 10.1002/cphc.202400314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 04/17/2024] [Indexed: 05/23/2024]
Abstract
Dissociative electron transfer in collisions between neutral potassium atoms and neutral ethanol molecules yields mainly OH-, followed by C2H5O-, O-, CH3 - and CH2 -. The dynamics of negative ions have been investigated by recording time-of-flight mass spectra in a wide range of collision energies from 17.5 to 350 eV in the lab frame, where the branching ratios show a relevant energy dependence for low/intermediate collision energies. The dominant fragmentation channel in the whole energy range investigated has been assigned to the hydroxyl anion in contrast to oxygen anion from dissociative electron attachment (DEA) experiments. This result shows the relevant role of the electron donor in the vicinity of the temporary negative ion formed allowing access to reactions which are not thermodynamically attained in DEA experiments. The electronic state spectroscopy of such negative ions, was obtained from potassium cation energy loss spectra in the forward scattering direction at 205 eV impact energy, showing a prevalent Feshbach resonance at 9.36±0.10 eV withσ O H * / σ C H * ${{\sigma }_{OH}^{^{\ast}}/{\sigma }_{CH}^{^{\ast}}}$ character, while a less pronouncedσ O H * ${{\sigma }_{OH}^{^{\ast}}}$ contribution assigned to a shape resonance has been obtained at 3.16±0.10 eV. Quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom have been performed to support the experimental findings.
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Affiliation(s)
- Ana Isabel Lozano
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
| | - Sarvesh Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
| | - Pedro J S Pereira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
- Department of Mathematics, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emídio Navarro 1, 1959-007, Lisboa, Portugal
| | - Boutheïna Kerkeni
- ISAMM, Université de la Manouba, La Manouba, 2010, Tunisia
- Département de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis, 2092, Tunisia
| | - Gustavo García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006, Madrid, Spain
| | - Paulo Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
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Kumar S, Hoshino M, Kerkeni B, García G, Limão-Vieira P. Isotope Effect in D 2O Negative Ion Formation in Electron Transfer Experiments: DO-D Bond Dissociation Energy. J Phys Chem Lett 2023; 14:5362-5369. [PMID: 37276433 PMCID: PMC10278136 DOI: 10.1021/acs.jpclett.3c00786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 05/31/2023] [Indexed: 06/07/2023]
Abstract
H2O/D2O negative ion time-of-flight mass spectra from electron transfer processes at different collision energies with neutral potassium yield OH-/OD-, O-, and H-/D-. The branching ratios show a relevant energy dependence with an important isotope effect in D2O. Electronic state spectroscopy of water has been further investigated by recording potassium cation energy loss spectra in the forward scattering direction at an impact energy of 205 eV (lab frame), with quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom supporting most of the experimental findings. The DO-D bond dissociation energy has been determined for the first time to be 5.41 ± 0.10 eV. The collision dynamics revealed the character of the singly excited (1b2-1) molecular orbital and doubly excited states in such K-H2O and K-D2O collisions.
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Affiliation(s)
- Sarvesh Kumar
- Atomic
and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Masamitsu Hoshino
- Department
of Materials and Life Sciences, Sophia University, Tokyo 102-8554, Japan
| | - Boutheïna Kerkeni
- ISAMM,
Université de la Manouba, La Manouba 2010, Tunisia
- Département
de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis 2092, Tunisia
| | - Gustavo García
- Instituto
de Física Fundamental, Consejo Superior de Investigaciones
Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - Paulo Limão-Vieira
- Atomic
and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
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Kumar S, Ben Chouikha I, Kerkeni B, García G, Limão-Vieira P. Bound Electron Enhanced Radiosensitisation of Nimorazole upon Charge Transfer. Molecules 2022; 27:molecules27134134. [PMID: 35807379 PMCID: PMC9268075 DOI: 10.3390/molecules27134134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/23/2022] [Accepted: 06/24/2022] [Indexed: 02/01/2023] Open
Abstract
This novel work reports nimorazole (NIMO) radiosensitizer reduction upon electron transfer in collisions with neutral potassium (K) atoms in the lab frame energy range of 10–400 eV. The negative ions formed in this energy range were time-of-flight mass analyzed and branching ratios were obtained. Assignment of different anions showed that more than 80% was due to the formation of the non-dissociated parent anion NIMO•− at 226 u and nitrogen dioxide anion NO2− at 46 u. The rich fragmentation pattern revealed that significant collision induced the decomposition of the 4-nitroimidazole ring, as well as other complex internal reactions within the temporary negative ion formed after electron transfer to neutral NIMO. Other fragment anions were only responsible for less than 20% of the total ion yield. Additional information on the electronic state spectroscopy of nimorazole was obtained by recording a K+ energy loss spectrum in the forward scattering direction (θ ≈ 0°), allowing us to determine the most accessible electronic states within the temporary negative ion. Quantum chemical calculations on the electronic structure of NIMO in the presence of a potassium atom were performed to help assign the most significant lowest unoccupied molecular orbitals participating in the collision process. Electron transfer was shown to be a relevant process for nimorazole radiosensitisation through efficient and prevalent non-dissociated parent anion formation.
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Affiliation(s)
- Sarvesh Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal;
| | - Islem Ben Chouikha
- Département de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis 2092, Tunisia;
| | - Boutheïna Kerkeni
- Département de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis 2092, Tunisia;
- ISAMM, Université de La Manouba, La Manouba 2010, Tunisia
- Correspondence: (B.K.); (P.L.-V.)
| | - Gustavo García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain;
| | - Paulo Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal;
- Correspondence: (B.K.); (P.L.-V.)
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