Coherence effects in the polarization of the light emitted by photofragments

In this paper a general quantum mechanical treatment of photodissociation and fluorescence from the fragments in the case of direct dissociation as well as in the case of photo-predissociation is presented. This formulation takes into consideration all the possible coherence effects coming from quantum interference between photodissociation amplitudes to different magnetic sublevels of the fragments. This results in large differences between classical and quantum results for the degree of polarization of the light emitted from photofragments. The theory is applied to the case of Ca2 which constitutes a striking experimental example of coherence effects in direct photodissociation. For this case the classical calculation predicts a polarization degree of 14 % while the experiment shows 64 %. The maximum theoretical value when coherence is taken into account is 78 %. The difference between the experimental result and the theoretical value is attributed to depolarization by saturation, although some other minor contribution may also be present. J. Physique 44 (1983) 1225-1245 NOVEMBRE 1983, Classification Physics Abstracts 33.80G 33.90