Modelling laser-atom interactions in the strong field regime

TL;DR

This paper develops a semi-analytical model for atomic hydrogen ionization in strong infrared fields, extending existing methods by using separable potentials and analyzing gauge issues, with results compared to the strong field approximation.

Contribution

The paper introduces a new semi-analytical model using separable potentials to better understand laser-atom interactions in the strong field regime, linking it to the strong field approximation.

Findings

The model accurately predicts electron energy spectra.

The role of excited states is clarified.

Comparison shows the model extends the strong field approximation.

Abstract

We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states.