Authors
Saikat Hazra, Soumya Mukherjee, Satrajit Adhikari
Published in
Physical chemistry chemical physics : PCCP. Aug 31, 2026. Epub Aug 31, 2026.
Abstract
This review elucidates the role of electron-nuclear coupling among low-lying electronic states in predicting photoelectron (PE), photoabsorption (PA), photodetachment (PD) and mass-analyzed threshold ionization (MATI) spectra of organic and inorganic molecules. Prototype systems, which include NO2, Na3, C6H4N2+, NO3, C6H6+, o-C6H4F2+ and 1,3,5-C6H3F3+, are examined to illustrate diverse nonadiabatic phenomena such as Jahn-Teller, pseudo-Jahn-Teller and Renner-Teller interactions. For this purpose, multi-state multi-mode diabatic Hamiltonians are systematically constructed from ab initio adiabatic potential energy surfaces and the corresponding nonadiabatic coupling terms via adiabatic-to-diabatic transformation (ADT). In this beyond Born-Oppenheimer (BBO) treatment, the existence of sub-Hilbert space is determined through quantization of nonadiabatic coupling terms and validity of curl condition. Once the diabatic Hamiltonians are constructed, time-dependent quantum dynamics employing the time-dependent discrete variable representation (TDDVR) method enable calculations of electronic state-resolved spectra, yielding good agreement with the experimental one in comparison with other theoretically calculated spectra. Since the BBO constructed path-dependent (non-unique) diabatic Hamiltonians are related through unitary transformation to each other, the calculated spectra appear to be unique for comparison with experimental results. Topological features of ADT angles and vibronic couplings with even-parity are interesting findings due to this "exact" approach.
PMID:
42669417
Bibliographic data and abstract were imported from PubMed on 31 Aug 2026.
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