Effects of Coriolis interaction on the rotational line intensities of symmetry-forbidden electronic transitions

The effect of Coriolis coupling on intensities in infrared rotation–vibration bands is here extended to vibronically allowed transitions between electronic states of a nearly symmetric top. Within the framework of the Herzberg–Teller treatment of vibronic interaction, equations are developed which describe the intensity distribution in the p- and r-form branches of a vibronic transition in the cases where Coriolis interaction perturbs one or both vibrational levels associated with the transition. The à 1A2–X̃ 1A1 transition in H2CO is used as an example to illustrate the theory.