Multiconfiguration self-consistent-field calculation of the dipole moment function of CO(X 1Σ+)

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Abstract
The dipole moment function for the 1Σ+ ground state of CO in the vicinity of the equilibrium internuclear distance has been calculated by the optimized valence configurations (OVC) multiconfiguration self‐consistent‐field method. The results are compared with existing Hartree‐Fock and configuration interaction treatments of this molecule at single points and also the dipole moment function deduced from experimental infrared intensities. At the experimental equilibrium separation, the calculated dipole moment is −0.167 D (C−O+) which is in reasonable agreement with the microwave value of −0.112 D (C−O+). The vibrationally averaged expectation value of the dipole moment based on the computed moment function and accurate vibrational wavefunctions is −0.151 D (C−O+) which is in better agreement with the observed microwave quantity and illustrates that the effect of vibrational averaging is not negligible in systems such as CO that possess small permanent dipole moments. A general prescription for constructing OVC wavefunctions for diatomic molecules is also presented.