AB-INITIO CALCULATION OF ROVIBRONIC TRANSITION SPECTRA OF CAH

The ground (1 (2) Sigma(+), X) and excited electronic states, 1 (2) Pi (A), 2 (2) Sigma(+) (B,B'), 1 (2) Delta, 2 (2) Pi (E), 3 (2) Sigma(+) (D), 4 (2) Sigma(+) (C), 5 (2) Sigma(+) (K), 3 (2) Pi (L), and 2 (2) Delta, of CaH are studied by ab initio calculation, with extensive con figuration interactions. Calculated spectroscopic constants, in partic ular, the excitation energies, are more accurate than in previous calc ulations and agree well with the currently available experimental data . This work confirms the existence of a single vibrational level, v'=4 , bound to the second well of the B state calculated from the experime ntal data by Martin [J. Chem. Phys. 88, 1797 (1988)]. Calculated oscil lator strengths for the B-X and D-X show irregular band structures bec ause of multiple avoided crossings of the potential energy curves. The avoided crossing between the D and C states should be taken into acco unt to explain the apparent perturbations observed in the experimental spectra. The wave functions, dipole moments, and transition dipole mo ments of these states are discussed in detail. (C) 1995 American Insti tute of Physics.