MULTICHANNEL QUANTUM-DEFECT THEORY OF DOUBLE-MINIMUM 1-SIGMA-G-ENERGYCURVES( STATES IN H2 .1. POTENTIAL)

Multichannel quantum-defect theory is applied to the highly accurate 1 SIGMA(g)+ ab initio excited-state potential-energy curves calculated b y Wolniewicz and Dressler [J. Chem. Phys. 82, 3262 (1985); and (privat e communication)]. We show that the three double-minimum states, EF, G K, and HH, can be represented to within 8 cm-1 by a smooth R-dependent 3 X 3 nondiagonal quantum-defect matrix. This quantum-defect matrix c orresponds to a collision of the Rydberg electron with the H-2(+)targe t, which may be in either the 1sigma(g) or 1sigma(u) state. Also discu ssed is the use of this quantum-defect matrix to calculate diabatic st ates, more highly excited Born-Oppenheimer states, and the electronic ionization width of the superexcited (1sigma(u))2 doubly excited state .