M. Gajda et al., IONIZATION OF AN EXCITED HYDROGEN-ATOM BY A HIGH-FREQUENCY CIRCULARLY-POLARIZED PULSED-FIELD, Physical review. A, 50(3), 1994, pp. 2528-2539
We study the ionization of atomic hydrogen by a high-frequency circula
rly polarized field. We solve numerically the time-dependent Schroding
er equation for the atomic wave function, which beforehand is expanded
in a Coulomb-Sturmian basis. We analyze the ionization from various i
nitial states differing by their azimuthal quantum number m, the princ
ipal and the angular quantum numbers being equal to 2 and 1, respectiv
ely. At high field intensities we observe important differences in the
ionization yield: strong stabilization is observed for m = 0 and m =
1 while for m = -1 the atom is almost completely ionized. We also stud
y the electron energy spectra for the same cases and show that they ar
e characterized by a multiple splitting of the above-threshold-ionizat
ion (ATI) peaks. The behavior of the ionization yield as well as the s
tructure observed in the ATI spectra are explained in terms of the ac-
Stark shift and width of the atomic levels. We also consider some of t
he aspects of the underlying dynamics by means of a very simple essent
ial-state model.