A simple method for polarizabilities and hyperpolarizabilities of alkali isoelectronic systems

A pseudopotential is introduced to make it possible to express the multipolar perturbed wavefunctions in terms of closed elementary functions. This pseudopotential is slightly different from the asymptotic Coulomb potential. This difference is accounted for in the final results with an interpolation procedure. Polarizabilities and hyperpolarizabilities of Li, Na, K, Rb, Cs, Be+, Mg+, Ca+, Sr+ and Ba+ are calculated with this method and are shown to be highly accurate. Particularly noteworthy is the simplicity of the third-order calculations which give the hyperpolarizabilities of the alkali series beyond Li.