Shifted 1/N expansion for the energy levels of laser-dressed Coulomb potential of the hydrogen atom

The recently developed shifted 1/N expansion technique, where N is the number of spatial dimensions, is applied to the study of the energy levels of the hydrogen atom in presence of intense laser radiation. The analytic expressions for the energy eigenvalues Esub(n,l)yield very accurate results for a wide range of n,l and the intensity-dependent truncation parameter lambda appearing in the effective laser-dressed binding potential. It is found that the level ordering satisfies Esub(n,l)>Esub(n,l') for l<l' and the energy eigenvalues scale down roughly as lambda-1 for large lambda. It is also observed that the convergence of the perturbation expansion improves remarkably with increasing intensity of the laser field. Finally the scope for extending the method to other areas of atomic physics is briefly discussed. (author)