Two-photon ionisation of atomic hydrogen in the presence of one-photon ionisation

Abstract

The authors propose a numerical method to calculate N-photon ionisation cross sections, when ionisation by N-1 photons is energetically possible. They present some results obtained for N=2. Cross sections obtained for two-photon ionisation of ns states of hydrogen by circularly polarised light are in excellent agreement with previous theoretical ones. As an example the method is also applied to lithium atoms.