Low-Energy Structures in Strong Field Ionization Revealed by Quantum Orbits

TL;DR

This paper demonstrates that incorporating Coulomb effects into quantum orbit models significantly improves the understanding and prediction of low-energy structures in strong field ionization spectra, aligning well with exact solutions.

Contribution

It introduces a Coulomb quantum orbit extension to the strong field approximation, providing a more accurate and physically intuitive description of low-energy ionization features.

Findings

Coulomb quantum orbits match TDSE results closely.

Enhanced interpretation of low-energy structures in ionization spectra.

Extension improves semi-classical models for strong field physics.

Abstract

Experiments on atoms in intense laser pulses and the corresponding exact ab initio solutions of the time-dependent Schr\"odinger equation (TDSE) yield photoelectron spectra with low-energy features that are not reproduced by the otherwise successful work horse of strong field laser physics: the "strong field approximation" (SFA). In the semi-classical limit, the SFA possesses an appealing interpretation in terms of interfering quantum trajectories. It is shown that a conceptually simple extension towards the inclusion of Coulomb effects yields very good agreement with exact TDSE results. Moreover, the Coulomb quantum orbits allow for a physically intuitive interpretation and detailed analysis of all low-energy features in the semi-classical regime, in particular the recently discovered "low-energy structure" [C.I. Blaga et al., Nature Physics 5, 335 (2009) and W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)].