ANALYTICAL APPROXIMATIONS FOR ADIABATIC AND NONADIABATIC MATRIX-ELEMENTS OF HOMONUCLEAR DIATOMIC RYDBERG STATES - APPLICATION TO THE SINGLET P-COMPLEX OF THE HYDROGEN MOLECULE

Closed expressions for the adiabatic and non-adiabatic matrix elements for coupling between the Rydberg states of diatomic molecules are der ived by a combination of single-channel quantum defect theory and semi classical mechanics. Validity conditions on the derived results and li miting behaviours as n --> infinity are discussed. Applications of the theory to low-lying B (1) Sigma(u)(+), B' (1) Sigma(u)(+) and C (1) P i(u), D (1) Pi(u) states of the singlet p-complex of hydrogen are in g ood agreement with ab initio results.