PNO-CI and CEPA studies of electron correlation effects - II. Potential curves and dipole moment functions of the OH radical

Abstract

Ab initio calculations of the potential curves of low laying electronic states of OH are performed on the basis of a variational configuration interaction wavefunction (PNO-CI) and the coupled electron pair approximation (CEPA). The latter approach yields a ground state potential curve which deviates from the RKR curve by less than 200 cm-1 in the region from 0.7 to 1.6 Å. Calculated ground state constants are as follows (experimental values in parentheses): re = 0.972 (0.971) Å, Be = 18.85 (18.87) cm-1, αe = 0.727 (0.714) cm-1, ωe = 3742 (3739) cm-1, ωeχe = 85.3 (86.4) cm-1, μ0 = 1.686 (1.66) D, De = 4.35 (4.63) eV,IP = 12.78 (13.36?) eV, El.Aff. = 1.51 (1.83) eV, v00(2Π↔2Σ+) = 32690(32440) cm-1. The correlation contributions to ionization, excitation and electron attachment are analyzed. On the basis of estimated CEPA-limits, which are in very good agreement with experiment for De and electron affinity, an IP of 13.0eV is recommended. Dipole moment expectation values and some IR transition probabilities are calculated from the ground state dipole moment curves. The calculated crossing point of the 2Σ- curve with the repulsive 4Σ- state is not in agreement with the position deduced from intensity data. © 1974 Springer-Verlag.