Burke Ritchie

Use of a modified Sternheimer method for achieving analytic, polynomial solutions to the equations of perturbation theory for multiphoton absorption by hydrogenic ions

A modified Sternheimer method is used to provide analytic, polynomial solutions to the equations of perturbation theory for multiphoton absorption by hydrogenic ions. The solutions are in the form of asymptotic series whose coefficients can be rapidly computed by means of two-term recursion formulas. These series eventually lead to divergent solutions as a function of photon energy; however, calculations show that accurate two-photon cross sections can be obtained for the entire excitation spectrum and for the ionization continuum to about 1250 \AA{}. Three-photon ionization cross sections are also calculated and these are shown to be accurate to about 2400 \AA{}.