Topological Effects in Vibronically Coupled Degenerate Electronic States: A Case Study on Nitrate and Benzene Radical Cation

• Published in: ACS omega Vol. 3; no. 10; pp. 12465 - 12475
• Main Authors: Mukherjee, Soumya, Mukherjee, Bijit, Dutta, Joy, Sardar, Subhankar, Adhikari, Satrajit
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 31.10.2018
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.8b01648

We carry out detailed investigation for topological effects of two molecular systems, NO3 radical and C6H6 + (Bz+) radical cation, where the dressed adiabatic, dressed diabatic, and adiabatic-via-dressed diabatic potential energy curves (PECs) are generated employing ab initio calculated adiabatic and diabatic potential energy surfaces (PESs). We have implemented beyond Born–Oppenheimer (BBO) theory for constructing smooth, single-valued, and continuous diabatic PESs for five coupled electronic states [J. Phys. Chem. A 2017, 121, 6314–6326]. In the case of NO3 radical, the nonadiabatic coupling terms (NACTs) among the low-lying five electronic states, namely, X̃ 2A2 ′ (12B2), Ã 2E″ (12A2 and 12B1), and B̃ 2E′ (12A1 and 22B2), bear the signature of Jahn–Teller (JT) interactions, pseudo JT (PJT) interactions, and accidental conical intersections (CIs). Similarly, Bz+ radical cation also exhibits JT, PJT, and accidental CIs in the interested domain of nuclear configuration space. In order to generate dressed PECs, two components of degenerate in-plane asymmetric stretching modes are selectively chosen for both the molecular species (Q 3x –Q 3y pair for NO3 radical and Q 16x –Q 16y pair for Bz+ radical cation). The JT coupling between the electronic states is essentially originated through the asymmetric stretching normal mode pair, where the coupling elements exhibit symmetric and nonlinear functional behavior along Q 3x and Q 16x normal modes.