Inversion isomerism induced by the Pseudo Jahn-Teller Effect in X₂CE molecules (X = H, F; E = O, S, Se) in their reduced and excited states

Abstract

The pseudo-Jahn-Teller effect (PJTE) is employed to reveal the origin of molecular geometry changes induced by reduction and excitation, using a series of X2CE molecules (X = H, F, Cl; E = C, S, Se) as examples. Their nuclear configuration is planar with C 2v symmetry in the ground electronic state. However, when reduced, they acquire a nonplanar pyramidal structure with an elongated C-E bond in their ground and lowest excited electronic states 1A2 and 3A2. It is shown that these distortions are due to the PJT mixing of the reference electronic states with appropriate excited states via the b 1 vibrational mode. The PJTE is shown to reasonably parametrize the adiabatic potential energy curve ε(Qb 1) along the instability coordinate Qb 1.