Multiconfiguration self-consistent-field calculation of the dipole moment function and potential curve of NO(X2Π)

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Abstract
The electronic dipole moment function, potential energy curve, and other one−electron properties of the 2Π ground state of NO have been calculated from R = 1.6 to R = 3.4 bohr by the optimized valence configurations (OVC) multiconfiguration self−consistent−field method. At internuclear separations only 0.6−0.7 bohr larger than Re, the ground state wavefunction is found to exhibit a nearly equal mixing of electronic configurations corresponding to the X2Π and B2Π states of NO. This behavior and its manifestations in the OVC framework are discussed in detail. The theoretical OVC−MCSCF dipole curve is shown to be consistent with available experimental data in that (1) its first derivative near Re of 1.10 D/bohr is in excellent agreement with that deduced from observed infrared intensities, and (2) the v = 0 dipole expectation value obtained from the computed moment function and accurate vibrational wavefunctions is −0.139 D (N−O+), which is within 0.02 D of the Stark effect microwave result of ±0.158 D. A comparison of the calculated potential curve with an accurate RKR potential for NO (X2Π) indicates relative congruency to within 0.06 eV over the full range of inernuclear separations spanning the turning points of the v = 25 vibrational level. Comparisons with previous theoretical treatments of this molecule are also presented.