Semiempirical calculation of van der Waals coefficients for alkali-metal and alkaline-earth-metal atoms

The van der Waals coefficients, C6 , C8, and C10 for the alkali-metal ~Li, Na, K, and Rb! and alkaline-earthmetal ~Be, Mg, Ca, and Sr! atoms are estimated by a combination of ab initio and semiempirical methods. Polarizabilities and atom-wall coefficients are given as a diagnostic check, and the lowest order nonadiabatic dispersion coefficient, D8 and the three-body coefficient, C9 are also presented. The dispersion coefficients are in agreement with the available relativistic many-body perturbation theory calculations. The contribution from the core was included by using constrained sum rules involving the core polarizability and Hartree-Fock expectation values to estimate the f-value distribution.