Anisotropy in Photofragmentation

Abstract

The past decade has seen intensive study of photoionization and photodissociation processes in atoms and molecules. The degree of experimental difficulty and the degree of theoretical sophistication needed to characterize a photofragmentation process both increase rapidly with the total number of correlated directions observed simultaneously. From this point of view the simplest processes involve only one direction, the incident photon polarization axis εˆ. For this class of processes the quantity of interest is the total cross section σ (or perhaps the isotropic partial cross sections σ_i. in alternative fragmentation channels i). The next step up in complexity involves two directions, the incident polarization axis and one other direction. For photofragment angular distributions the second axis is of course Kˆ, the escape axis of the separating fragments. Another class of experiments in which just two directions are relevant is the class of alignment and orientation experiments. In these a photon, emitted after the photoeffect has produced an excited fragment state, is observed along some axis Kˆʹ, thereby providing the second direction.