Shape Resonances and Rotationally Predissociating Levels: The Atomic Collision Time-Delay Functions and Quasibound Level Properties of H2(X Singlet Sigma(G)(+))

摘要

The energy dependence of the collisional time-delay function was computed for H(1S) atoms interacting via the ab initio H2(X singlet Sigma(g)(+)) potential. Peaks in this function determine the scattering resonance energies E(r) and widths Gamma, and the lifetimes for each of the corresponding quasibound vibrational-rotational levels. Small differences are found between these E(r) and Gamma, and the values obtained by a 'maximum internal amplitude' approach (intended to characterize the spectroscopically observable predissociating levels). Approximate procedures for rapid, accurate numerical evaluation of E(r) are appraised; a new outer-boundary-condition criterion for resonances leads to the best agreement with the exact results. For ground-state H2, HD and D2, the onset of line broadening due to centrifugal barrier penetration is found to occur at energies some hundreds of 1/cm below the locus of barrier maxima. (Author)