Above threshold ionization of atomic hydrogen in ns states with up to four excess photons

E Karule (1) , A Gailitis (2)

1 Institute of Physics and Spectroscopy
2 LU - University of Latvia

In a high intensity laser field an atom can absorb more photons than the minimum necessary for ionization. It is known as above threshold ionization (ATI). Theoretically it is the most difficult case to handle as we have to consider transitions in continuum. To study ATI we use the perturbation theory and the Green's function formalism. We have derived the modified two-term Coulomb Green's function (CGF) Sturmian expansion. In each term explicit summation over all intermediate states is carried out. The transition amplitude may be obtained in a closed form. The generalized cross sections are evaluated for the photoionization of atomic hydrogen in ns states with up to four excess photons. Calculations are performed in the wide range of wavelengths for linear and circular polarization. In the cases for which data is available our results agree very well with previous ones. Above threshold ionization of atomic hydrogen in ns states 2

Mots clés: 32.80Fb; 32.80.Rm; 31.15.xp; 31.15.-p

E Karule, A Gailitis. Above threshold ionization of atomic hydrogen in ns states with up to four excess photons. Journal of Physics B: Atomic, Molecular and Optical Physics, 2010, 43 (6), pp.65601. ⟨10.1088/0953-4075/43/6/065601⟩. ⟨hal-00569890⟩