The effect of protonation on the photodissociation processes in formamide - An ab initio surface hopping dynamics study

Photodeactivation processes of protonated formamide were investigated using the multireference configuration interaction calculations with singles and doubles (MR-CISD) method while dynamics were simulated by employing the mixed quantum-classical direct trajectory method with surface hopping based on multi-configurational self-consistent wave functions. The dynamics calculations from the first excited singlet state in O-protonated formamide resembled those found for the second valence excited state of the parent molecule. Two deactivation processes were found: the C-N (major) and C-O (minor) dissociations with very short lifetimes (33 fs). Similarly, the major process for photodecomposition in the first excited state of N-protonated formamide resembles that for the parent formamide, and involves C-N dissociation with a lifetime around 390 fs. However, 55% of trajectories remained undissociated and undeactivated until 1000 fs, indicating the existence of other deactivation processes on a longer time scale.