MULTICHANNEL QUANTUM-DEFECT THEORY OF DOUBLE-MINIMUM 1-SIGMA-G-ENERGYLEVELS( STATES IN H2 .2. VIBRONIC)

In the preceding paper [Phys. Rev. A 49, 4353 (1994)] we obtained the quantum-defect matrix of the strongly interacting double-minimum state s of H, by fitting to the ab initio clamped-nuclei electronic energies of Wolniewicz and Dressler [J. Chem. Phys. 82, 3292 (1985), and priva te communication]. Yu, Dressler, and Wolniewicz have calculated the vi bronic energies of the corresponding states using an approach involvin g the state-by-state evaluation of vibronic coupling, and the solution of a set of coupled equations. Here we calculate the vibronic energie s using our quantum-defect matrix in a version of scattering theory kn own as multichannel quantum-defect theory (MQDT). This less traditiona l treatment involves both singly and doubly excited channels and repro duces the vibronic energies to almost the same precision as the couple d-equations approach. In addition, several refinements have been made to MQDT.