FEMTOSECOND TIME-RESOLVED MASS AND PHOTOELECTRON SPECTROSCOPIC STUDY OF OCLO PHOTODISSOCIATION - COHERENT ENERGY-TRANSFER IN A STEPWISE REACTION

Femtosecond time resolved mass spectroscopy (TRMS) and photoelectron s pectroscopy (TRPES) are applied to the study of OClO photodissociation near 3.21 eV of excitation. The reaction is found to proceed in two s teps: a slow approach to an intermediate state (time constant = 4.6 ps ) which falls apart in 250 fs. Pronounced vibrational coherence is obs erved in the TRMS/PES of OClO. Weak coherence is also observed in the TRMS of ClO but not in the corresponding PES. The observation is consi stent with a mechanism that the vibrational coherence survives a slow surface-crossing reaction, then is destroyed during fragmentation. (C) 1997 Elsevier Science B.V.