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

摘要

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, $\tilde{X}$²A2^′ (1²B2), A~²E″ (1²A2 and 1²B1), and B~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 selectivelychosen for both the molecular species (Q3x–Q3y pair for NO3 radical and Q16x–Q16y pair for Bz⁺ radical cation). The JTcoupling between the electronic states is essentially originated throughthe asymmetric stretching normal mode pair, where the coupling elementsexhibit symmetric and nonlinear functional behavior along Q3x and Q_16x normal modes.