Frustrated tunneling dynamics in ultrashort laser pulses

TL;DR

This paper models frustrated tunneling ionization in ultrashort laser pulses using a strong field approximation and saddle point methods, comparing results with quantum simulations to identify areas for improvement.

Contribution

It introduces a quasiclassical model for frustrated tunneling ionization and analyzes saddle point solutions, highlighting discrepancies with quantum results for detailed angular momentum states.

Findings

Qualitative agreement in principal quantum number populations

Inconsistent angular momentum channel populations between model and TDSE

Identifies need for improved trajectories for quantitative accuracy

Abstract

We study a model for frustrated tunneling ionization using ultrashort laser pulses. The model is based on the strong field approximation and it employs the saddle point approximation to predict quasiclassical trajectories that are captured on Rydberg states. We present a classification of the saddle-point solutions and explore their behavior as functions of angular momentum of the final state, as well as the carrier--envelope phase (CEP) of the laser pulse. We compare the final state population computed by the model to results obtained by numerical propagation of the time-dependent Schr\"odinger equation (TDSE) for the hydrogen atom. While we find qualitative agreement in the CEP dependence of the populations in principal quantum numbers, $n$, the populations to individual angular momentum channels, $\ell$, are found to be inconsistent between model and TDSE. Thus, our results show that improvements of the quasiclassical trajectories are in order for a quantitative model of frustrated tunneling ionizaiton.