We determine generalized cross sections for two-photon double ionization of He in the photon energy region between 40.7 and 47 eV where absorption of two photons can lead to non-sequential double ionization only. The present cross sections, obtained in R-matrix Floquet theory, agree with cross sections obtained from time-dependent calculations. By examining the ratio of two-photon double ionization to two-photon single ionization, we demonstrate that core excitation effects at an intensity of 10(13) W cm(-2) are relatively unimportant at 45 eV, but that they are significant at other photon energies.
|Number of pages||7|
|Journal||Journal of Physics B: Atomic Molecular and Optical Physics|
|Publication status||Published - 14 Jan 2003|
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Atomic and Molecular Physics, and Optics