Photodissociation and rotational coherence

The rotational coherence of an ensemble of photodissociation fragments is studied in the absence of collisions. Formulas for quantum orientation correlation functions are obtained for the case when parent molecules and their fragments are asymmetric tops and the predissociation time is much shorter than the characteristic time of rotational reorientation. It is shown that photodissociation does not affect periods of a rotational echo, but the structure of the echo pulses (their shape and width) depends substantially on the features of rotational excitation of photofragments upon photodissociation.