Theoretical determination of the ionization cross-section of water.
Résumé
For H2O taken as a model, a comparison is made between three approaches generally used for the detn. of photoionization cross-section profile. The wave function results from an ab initio multiconfigurational calcn. The plane wave (PW) model including ionic core correlation leads to a good interpretation of the photoionization spectra and energy photon dependence is analyzed. In a L2 approach assocd. with the Stieltjes moment method, a comparative study of two basis sets leads us to appreciate the resp. importance of Rydberg and polarization functions. The last point of our work is devoted to the calcn. of photoionization cross-section from the inversion of the Kramers-Kronig dispersion integral in a gauge invariant model. This approach allows to underline the importance of the pseudo states in the continuum discretization