The Rydberg spectrum of CaF and BaF: Calculation by R-matrix and generalized quantum defect theory

R-matrix theory combined with generalized quantum defect theory is used to calculate the electronic spectrum of the CaF and BaF molecules from the ground state up near the ionization limit. The approach, an effective one-electron method similar in spirit to the ligand-field model of Rice, Martin. and Field [S. F. Rice, H. Martin, and R. W. Field, J. Chem. Phys. 82, 5023 (1985)] and to the electrostatic polarization model of Torring, Ernst. and Kandler [T. Torring, W. E. Ernst, J. Kandler, J. Chem. Phys. 90, 4927 (1989)] removes many of the limitations inherent in the previous work. The resulting level energies (effective principal quantum numbers) are in good agreement with the available experimental data and constitute the first quantitative theoretical calculation of the full electronic spectrum of CaF and BaF. Limitations and possible extensions of the theory are discussed, and quantum defects of high orbital angular momentum states are predicted. (C) 1997 American Institute of Physics.