Higher – Order Dispersion Potential Coefficient C12 for H and Alkali – Metal Atoms Interactions

This work is introduced to calculate the higher – order dispersion (van der Waals) potential coefficient C12 which is resulting from the second – order perturbation theory , this study was applied for H and alkali – metal atoms in the ground and first excited energy S-state .The dispersion potential coefficient was computed for all possible homonuclear and hetronuclear systems combinations of these atoms . The higher – order dispersion potential coefficient C12 requires to derive the dynamic polarizability equation of high degree of polarity (hexadecapole : L=4) (a 16 ) iw , which is derived from the general formula of the dynamic perturbed energy (for L=4) . We used a pseudopotential model to describe the motion of the valence electron in the field of closed core of alkali – metal atoms ,that, will be useful to compute the radial wave functions in the dynamic hexadecapole polarizability equation. The dynamic hexadecapole polarizability formula used to calculate the static hexadecapole polarizability (a 16) o at w=0, to evaluate the higher – order effective transition frequencies w4 and corresponding effective oscillator strengths fi , then, consequently , all of these parameters contribute in the calculation of final form of the higher - order dispersion potential coefficient C12.The present numerical results were compared with other researchers in the groundenergy state.