Diagrammatic Perturbation Theory: Potential Curves for the Ground State of the Carbon Monoxide Molecule

Diagrammatic many-body perturbation theory is used to calculate the potential energy function for the X(1)Sigma(+) state of the CO molecule near the equilibrium nuclear configuration. Spectroscopic constants are derived from a number of curves which are obtained from calculations taken through third order in the energy. By forming [2/1] Pade approximants to the constants we obtain: r(e) = 1.175 angstrom (1.128 angstrom), B(e) = 1.943 cm(-1) (1.9312 cm(-1)), alpha(beta)(e) = 0.0156 cm(-1) (0.0175 cm(-1)), omega(e) = 2247 cm(-1) (21 70 cm(-1)), omega(e)chi(e), = 12.16 cm(-1) (13.29 cm(-1)), where the experimental values are given in parenthesis.