Quantum dynamics of vibrational overtone induced photodissociation of a model polyatomic

The detailed processes, including state preparation, intramolecular energy transfer, and unimolecular reaction, are studied for the dissociation of a model molecule by tuning an intense laser to transitions in the vicinity of local mode overtone states. Photochemical yields are calculated quantum mechanically for a range of frequencies and pulse times, by combining the method of complex coordinates with the time-dependent interaction representation. Yields for long pulse times are dominated by the absorption cross section at each frequency, which is in turn dominated by the transition moment for the eigenstate to which the laser is tuned. As a consequence, we observe the result that more reactive states actually can produce smaller photochemical yields. With shorter pulses (0.1 to 10 ps), the yield is a sensitive function of both frequency and pulse time. By mapping out the photochemical yield as a function of both pulse time and excitation frequency, the details of the photodecay process are revealed.