Femtosecond time-resolved mass and photoelectron spectroscopic study of OC1O photodissociation. Coherent energy transfer in a stepwise reaction

Femtosecond time resolved mass spectroscopy (TRMS) and photoelectron spectroscopy (TRPES) are applied to the study of OC1O photodissociation near 3.21 eV of excitation. The reaction is found to proceed in two steps: a slow approach to an intermediate state (time constant = 4.6 ps) which falls apart in 250 fs. Pronounced vibrational coherence is observed in the TRMS/PES of OC1O. Weak coherence is also observed in the TRMS of C1O but not in the corresponding PES. The observation is consistent with a mechanism that the vibrational coherence survives a slow surface-crossing reaction, then is destroyed during fragmentation.