Coherence effects in the polarization of photofragments

Abstract

The general quantum-mechanical treatment of coherence effects in the polarization of the fluorescence, as well as in the orientation of photofragments, is reviewed. They are the result of simultaneous excitation of dissociative electronic states with different symmetry correlating to the same limit. The coherent excitation produces interferences which depend both on the photoabsorption probability amplitudes as well as on the relative phases of the continuum vibrational wavefunctions at large distances. Oscillations in the polarization degree of photofragments fluorescence as a function of the photon energy are predicted. Examples are presented in the case of direct dissociation of diatomic molecules. The case of slow predissociation is also analysed. Finally, possible extensions to the photodissociation of polyatomic molecules are considered.