Polarized Fluorescence of Fragments in a Gas Phase and the Mechanism of Photodecay: II. Relaxation of Anisotropy

摘要

The decay kinetics of fluorescence anisotropy of photofragments is studied in the reaction A + hV_(abs) -> B~* + products, B~* -> B hV_(em) under collisionless conditions in the presence of rotational dissociation. It is shown that the nonmonotonic decay of fluorescence anisotropy also occurs in the absence of the additional angular momentum #DELTA# caused by anisotropy of the interfragment potential, whereas for large #DELTA# the alternating oscillations of an anisotropy appear with a period inversely proportional to #DELTA#. Predissociation results in a noticeable decrease in the amplitude of oscillations. It is found that if rotation of initial molecules makes a dominant contribution to rotation of fragments (#DELTA# is small), then the part of the angular momentum of the initial molecule transferred to the fragment is scaled by the ratio of the inertia moment of the fragment to that of the initial molecule, resulting in a slower decay of anisotropy as compared to the case of free fragments.