SPIN-ELECTRONIC-ROTATIONAL FRAME TRANSFORMATION FOR PHOTOIONIZATION AND RYDBERG SPECTRA OF DIATOMIC-MOLECULES

The spin-rotational-electronic fine structure of molecular Rydberg and continuum states is considered. The frame transformation from the lab oratory frame [Hund's case (e)] to the molecular frame [Hund's case (a )] is derived. Symmetry requirements are fully incorporated into the t ransformation, thus facilitating its practical use. Expressions for th e dipole transition amplitudes in Hund's case (a), again fully symmetr ized, are given, as well as their transformation to Hund's case (e) ap propriate for excitation to discrete Rydberg states and the ionization continuum. Various examples of the transformation within the framewor k of collision theory and of multichannel quantum defect theory are de scribed, and it is shown how the general frame transformation reduces to the transformations for molecules without electron spin. The presen t formulation can also be applied to the photoionization of aligned an d oriented molecules, as well as to ''complete'' experiments.