Intra- and intercycle interference of angle-resolved electron emission in laser assisted XUV atomic ionization

TL;DR

This paper presents a semiclassical model to analyze angle-resolved electron emission in laser-assisted XUV atomic ionization, accurately capturing interference patterns and surpassing traditional approximations.

Contribution

The study introduces a semiclassical approach that effectively describes intra- and intercycle interference in angle-resolved photoelectron spectra, improving upon existing theories.

Findings

The model accurately predicts interference patterns in electron emission.

Intercycle and intracycle interferences modulate the photoelectron spectrum.

The approach agrees with TDSE and strong field approximation results.

Abstract

A theoretical study of ionization of the hydrogen atom due to an XUV pulse in the presence of an IR laser is presented. Well-established theories are usually used to describe the problem of laser assisted photoelectron effect. However, the well-known soft-photon approximation firstly posed by Maquet et al in Journal of Modern Optics 54, 1847 (2007) and Kazansky's theory in Phys. Rev. A 82, 033420 (2010) completely fails to predict the electron emission prependicularly to the polarization direction. Making use of a simple semiclassical model, we study the angle-resolved energy distribution of photoelectrons for the case that both fields are linearly polarized in the same direction. We thoroughly analize and characterize two different emission regions in the angle-energy domain: (i) the parallel-like region with contribution of two classical trajectories per optical cycle and (ii) the perpendicular-like region with contribution of four classical trajectories per optical cycle. We show that our semiclassical model is able to asses the interference patterns of the angle-resolved photoelectron spectrum in the two different mentioned regions. Electron trajectories stemming from different optical laser cycles give rise to angle-independent intercycle interference known as sidebands. These sidebands are modulated by an angle-dependent coarse-grained structure coming from the intracycle interference of the electron trajectories born during the same optical cycle. We show the accuracy of our semiclassical model as a function of the time delay between the IR and the XUV pulses and also as a function of the laser intensity by comparing the semiclassical predictions of the angle-resolved photoelectron spectrum with the continuum-distorted wave strong field approximation and the ab initio solution of the time dependent Schr\"{o}dinger equation.