Time-domain theory of atomic photoionization

TL;DR

This paper investigates atomic photoionization in the time domain, revealing how photoelectron wave packets evolve rapidly and providing insights beyond traditional time delay measurements, especially for few-cycle laser pulses.

Contribution

It combines numerical and theoretical methods to analyze the shape evolution of photoelectron wave packets and highlights effects of pulse duration on photoelectron velocity.

Findings

Wave packet shape changes from multi-peak to single-peak after emission

Time-domain analysis reveals additional information beyond average position

Few-cycle pulses alter the asymptotic velocity of photoelectrons

Abstract

We present a combined numerical and theoretical study of atomic photoionization in the time domain. We show how a photoelectron wave packet rapidly changes its shape after being emitted, from a complex multi-peak structure to eventually a relatively simple single-peak structure. This time-domain shape evolution provides information beyond the time-dependent average position of the wave packet, which has been used to retrieve the Wigner time delay. For few-cycle laser pulses, the asymptotic velocity of the photoelectron can be different from long-pulse-based expectations due to non-negligible changes of the dipole matrix element within the spectra of the laser pulses.