MULTICHANNEL QUANTUM-DEFECT THEORY AND DOUBLE-RESONANCE SPECTROSCOPY OF AUTOIONIZING LEVELS OF MOLECULAR-HYDROGEN

Multichannel quantum defect theory has been used to calculate vibrational and rotational branching ratios in the photoionization of H-2 excited to the E,F (1) Sigma(g)(+) state. The calculations take into account the interaction with doubly excited channels in the E,F (1) Sigma(g)(+) lower state, the energy and R dependence of the transition to the upper state, and the rovibronic channel interactions in the final states. The input data consist of the ionic potential energy curves and the known R-dependent quantum defects for the gerade and ungerade channels of H-2. All these parameters are used without adjustment. The theoretical results are compared with the results of earlier double-resonance experiments. This detailed comparison shows that the R dependence of the transition dipole moments has considerable influence on the resonance profiles and the branching ratios. The overall agreement with the experimental results is excellent, and most of the observed discrepancies can be accounted for by the competing decay processes of predissociation and fluorescence, which were not included in the calculations.