Theoretical study of the electron correlation and excitation effects on energy distribution in photon impact ionization

We performed a detailed theoretical study of the electron correlation and core excitation effects on the energy distribution of the ejected electrons in the process of photon impact tunnel ionization. We used the Landau-Dykhne approach to obtain analytical formulas for the transition rate and the energy distribution with included these effects. We have limited ourselves to a non-relativistic domain, in which the rate and distribution are determined by the electrical component of the laser field, while the influence of magnetic one can be neglected. We observed helium and helium like atoms. We have shown that the tunneling ionization mechanism may be understood as the combination of mentioned processes. We considered the case of a monochromatic wave with an elliptically polarized laser field. We compared our results with experimental and shown that ellipticity plays an important role and that inclusion of additional processes significantly influences the transition rate, as well as the energy distribution of the ejected photoelectrons.