Investigating the hydrogen atom in crossed external fields by the method of moments

Recurrence relations of perturbation theory for the hydrogen ground state a re obtained. With the aid of these relations, polarizabilities in constant mutually perpendicular electric and magnetic fields are computed up to the 80th order of perturbation theory. The high-order asymptotic expression is compared with its semiclassical estimate. For the case of an arbitrary rela tive orientation of external fields, a general sixth-order formula is given . The energy and the width of the ground state are obtained by means of a p erturbation-series summation. (C) 2000 MAIK "Nauka/Interperiodica".