# The effect of Coulomb field on laser-induced ultrafast imaging methods

## TL;DR

This study reveals that the ionic Coulomb field significantly influences high-order above-threshold ionization spectra, especially near the cutoff, challenging previous assumptions in laser-induced electron diffraction methods and affecting imaging accuracy.

## Contribution

It demonstrates the dominant role of 3rd-return-recollision trajectories in HATI spectra and highlights the need to consider Coulomb effects in laser-induced imaging techniques.

## Key findings

- 3rd-return-recollision trajectories dominate near the cutoff
- Coulomb field alters electron beam characteristics
- Implications for improving laser-induced imaging accuracy

## Abstract

By performing a joint theoretical and experimental investigation on the high-order above-threshold ionization (HATI) spectrum, the dominant role of the 3rd-return-recollision trajectories in the region near the cutoff due to the ionic Coulomb field is identified. This invalidates the key assumption adopted in the conventional laser-induced electron diffraction (LIED) approach that the 1st-returnrecollision trajectories dominate the spectrum according to strong field approximation (SFA). Our results show that the incident (return) electron beams produced by the 1st and 3rd returns possess distinct characteristics of beam energy, beam diameter and temporal evolution law due to the influence of Coulomb field, and therefore the extracted results in the LIED will be altered if the significance of the 3rd-return-recollision trajectories is properly considered in the analysis. Such Coulomb field effect should be taken into account in all kinds of laser-induced imaging schemes based on recollision.