Padé-Approximant Studies of Long-Range Forces

Abstract

Two-point Padé approximants of the dynamic polarizabilities are used to calculate the leading term of the long-range (van der Waals) force between atoms. The bounding properties of these approximants are established explicitly. A successive-approximation procedure is introduced. It keeps each step simple and makes the higher-order approximation expressible in closed forms and readily applicable. The results of hydrogen and noble gases show that, with the known moments, the present method gives the tightest upper and lower bounds yet established.