Coulomb time delays in high harmonic generation

TL;DR

This paper derives general expressions for ionization and recombination times in high harmonic generation, highlighting their differences from traditional photo-electron spectroscopy times, and compares theoretical calculations with experimental data.

Contribution

It provides the first rigorous derivation of ionization and recombination times specific to high harmonic generation experiments, linking them to existing measurement protocols.

Findings

Derived general expressions for ionization and recombination times in HHG.

Showed these times differ from photo-electron spectroscopy times.

Compared theoretical calculations with experimental results.

Abstract

Measuring the time it takes to remove an electron from an atom or molecule during photoionization using newly developed attosecond spectroscopies has been a focus of many recent experiments. However, the outcome of such measurement depends on measurement protocols and specific observables available in each particular experiment. One of such protocols relies on high harmonic generation. First, we derive rigorous and general expressions for ionization and recombination times in high harmonic generation experiments. We show that these times are different from, but related to ionization times measured in photo-electron spectroscopy, i.e. using attosecond streak camera, RABBITT and atto-clock methods. Second, we use the Analytical R-Matrix theory (ARM) to calculate these times and compare them with experimental values.