Intramolecular energy transfer and predissociation in C‐state HCN

Using our ab initio configuration interaction potential energy surface for the C state of HCN, we carried out classical trajectory calculations aimed at simulating the predissociation dynamics of various vibronic states of HCN and DCN. Our results provide an interpretation of the experimental photofragment excitation spectrum of this species. They also indicate that tunneling, which had been postulated as a rate‐determining step in the predissociation, is not substantial. Intramolecular energy transfer seems to be the slow step. Finally, there is evidence that on a time scale up to one rotational period, the predissociation kinetics is quite mode specific.