Molecular properties from MCSCF-SCEP wave functions. I. Accurate dipole moment functions of OH, OH−, and OH+

Potential energy and dipole moment functions for the ground states of OH, OH−, and OH+ have been calculated from MCSCF, MCSCF-SCEP, and SCEP-CEPA electronic wave functions. The stability of the dipole moments with respect to the number of configurations (up to 598) and orbitals (up to 14) simultaneously optimized in the MCSCF procedure and the number of reference configurations (up to 11) in the MCSCF-SCEP wave functions (up to 69 830 configurations) has been investigated. The dipole moment functions obtained from the best electronic wave functions are more accurate than all previously calculated ones. The deficiencies of the former calculations have been critically analyzed. The OH− and OH+ ions are predicted to be stronger IR emitters than the neutral OH radical. The rotationless rates of spontaneous emission A10 for the fundamental transitions are calculated to be 12.2, 137, and 263 s−1 for OH, OH−, and OH+, respectively. The calculated dipole moments in the vibrational ground states are 1.65, 1.04, and 2.32 D, respectively.