Resonance contributions to the photoionization spectrum of atomic hydrogen in an electric field.

Abstract

The photoionization cross section of hydrogen in an electric field is calculated as the sum of resonance contributions, apart from background. Each contribution is proportional to the imaginary part of the square of a complex transition-dipole matrix element divided by an energy denominator and has an asymmetric line shape that is the superposition of dispersive and absorptive Lorentzians. The main features of experiments on the ground and n=2 states, including asymmetry of the lines and blue shift of maxima with respect to calculated resonances near zero energy, are reproduced ab initio. .AE