A study of spin–orbit vibronic-coupling effects in the state of CCX (X = O, S, Se) and CNY (Y = N, P, As)

The vibronic structure of the A ∼ 3 Π excited electronic state of CCX (X = O, S, Se) and CNY (Y = N, P, As) has been calculated by considering Renner–Teller coupling together with spin–orbit coupling. The vibronic and spin–orbit coupling parameters have been determined by accurate ab initio electronic-structure calculations. The effect of the linear (in the bending mode) spin–orbit coupling mechanism [S. Mishra et al., J. Chem. Phys. 126 (2007) 134312] on the vibronic structure of the 3Π electronic state has been discussed. The vibronic structures of the A ∼ 3 Π electronic state of CCSe and CNAs are found to exhibit pronounced perturbations due to the linear spin–orbit coupling term.