Koopmans' Theorem and Selection Rules for One-Electron Ionization Processes in Orbitally Degenerate Systems Full article
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Journal of Chemical Physics
ISSN: 0021-9606 , E-ISSN: 1089-7690 |
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| Output data | Year: 2022, Volume: 157, Number: 17, Article number : 174103, Pages count : 14 DOI: 10.1063/5.0110124 | ||
| Tags | Koopmans' theorem; Photoelectron spectroscopy; Selection rule; Restricted open-shell Hartree-Fock | ||
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Funding (1)
| 1 | Ministry of Science and Higher Education of the Russian Federation | 0239-2021-0009 |
Abstract:
One-electron ionization processes X→Xi+ in orbitally degenerate systems, such as atoms with the open-shell configuration pN, can be divided into two groups. The first group involves those processes which are allowed in photoelectron spectra. The processes of this group in atoms obey the familiar selection rules (SRs) formulated within the Russell-Saunders L,S coupling. All other ionization processes, for which SRs are not obeyed, belong to the second group. Here we analyze the validity of Koopmans' theorem (KT) for processes of the second group forbidden by SRs. We show that the general formulation of KT in the Hartree-Fock method [Plakhutin, J.Chem.Phys. 148, 094101 (2018)] is implicitly based on the assumption that a X→Xi+ process is allowed by SRs, and this presents a limitation of KT. To overcome the latter, we prove that the variational condition underlying KT gives different results for SR-allowed and SR-forbidden processes. For the former processes, this condition gives the familiar KT relationship Ii = -εi , while for SR-forbidden processes the respective relationship between Ii and εi takes a more complex form. The practical applicability of the present extension of KT is verified by applying it to the totality of ionization processes in the valence 2s and 2p shells of atoms C, N, and O in their ground and excited states, that involves in all 29 SR-allowed and 34 SR-forbidden processes. For all of these processes, we compare KT estimates of ionization energies (IEs) with the relevant experimental data. For completeness, we also present ΔSCF estimates of IEs.
Cite:
Plakhutin B.N.
Koopmans' Theorem and Selection Rules for One-Electron Ionization Processes in Orbitally Degenerate Systems
Journal of Chemical Physics. 2022. V.157. N17. 174103 :1-14. DOI: 10.1063/5.0110124 WOS Scopus РИНЦ AN PMID OpenAlex
Koopmans' Theorem and Selection Rules for One-Electron Ionization Processes in Orbitally Degenerate Systems
Journal of Chemical Physics. 2022. V.157. N17. 174103 :1-14. DOI: 10.1063/5.0110124 WOS Scopus РИНЦ AN PMID OpenAlex
Dates:
| Submitted: | Jul 15, 2022 |
| Accepted: | Oct 3, 2022 |
| Published online: | Oct 4, 2022 |
| Published print: | Nov 1, 2022 |
Identifiers:
| Web of science: | WOS:000884800300005 |
| Scopus: | 2-s2.0-85141512199 |
| Elibrary: | 50518947 |
| Chemical Abstracts: | 2022:2811149 |
| PMID: | 36347678 |
| OpenAlex: | W4300979852 |
Citing:
| DB | Citing |
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| Elibrary | 1 |