An analytic approach to the hydrogen Stark effect in weak, strong, and ultrastrong fields

Abstract
An accurate analytic approximate solution of the hydrogen-Stark-effect Schrödinger equation is obtained. In contrast to previous non-numerical solutions, this solution (which is piecewise continuous, and easily calculable) is accurate for applied electric fields of arbitrary strength—including weak fields (F0.1Fion; the Stark-shift regime), strong fields (FFion), and ultrastrong fields (F102Fion), where Fion=3×108 V / cm is the classical ionization field of hydrogen. The ultrastrong-field regime is experimentally accessible in solid-state physics where, for hydrogenic excitons, Fion may be as small as 102 V / cm.