Unitary model for atomic ionization by intense XUV laser pulses

TL;DR

This paper introduces a unitary model for atomic ionization under intense XUV laser pulses, accurately capturing initial state dynamics and electron spectra with simplified equations, validated against full Schrödinger solutions.

Contribution

The paper presents a novel unitary model that fully accounts for initial state coupling in atomic ionization by intense laser pulses, providing both exact and approximate solutions validated against Schrödinger equation results.

Findings

Model accurately predicts initial state population dynamics.

Electron energy spectra are well reproduced by the model.

Approximate solutions closely match numerical results.

Abstract

A unitary model describing the electronic transitions in an atom subject to a strong high frequency laser pulse is proposed. The model fully accounts for the initial state coupling with the continuum spectrum. Continuum-continuum as well as discrete-discrete transitions are neglected. The model leads to a single integro-differential equation for the initial state amplitude. Exact numerical and approximate closed semi-analytical solutions of this equation are obtained. A comparison of present results with full time dependent Schr\"odinger equation solution for Hydrogen atoms subject to a laser pulse is presented. The initial state time dependent population is rather well described by the model and two approximate solutions. The electron energy spectrum is also well reproduced by the model and by a new improved Weiskopf-Wigner related approximation.