Dissociation of a diatomic molecule to atomic fine structure states: Electronically nonadiabatic effects upon resonant two-photon dissociation

We present the theory for two photon photodissociation of diatomic molecules into atomic fragments with nonvanishing angular momentum. Hund's cases (a) and (b) and any coupling scheme between them are explicitly treated. Various axial recoil limit approximations are derived in the limit for large fragment translational energy and are shown to simplify the description of the photodissociation. Expressions are derived for integral and differential photodissociation cross sections, for angular distributions of the fluorescence from excited atomic fragments, and for combined differential cross section and fluorescence photon angular distributions following the two photon dissociation. Anisotropy parameters and branching ratios in the J-independent axial recoil limit depend only on the symmetry of the molecular electronic states involved in the dissociation and on the atomic term limit. We tabulate these quantities for some common molecular electronic state symmetries and atomic term limits.