# Near-threshold photoelectron holography beyond the strong-field approximation

## TL;DR

This paper introduces a Coulomb quantum-orbit strong-field approximation (CQSFA) to analyze near-threshold photoelectron holography, revealing how Coulomb effects shape low-energy interference structures in photoelectron angular distributions.

## Contribution

The study develops a new CQSFA method that accurately models near-threshold photoelectron holography beyond the strong-field approximation, explaining the fan-shaped interference pattern.

## Key findings

- CQSFA agrees well with time-dependent Schrödinger equation results.
- The fan-shaped structure arises from Coulomb-influenced quantum interference.
- Coulomb potential significantly affects electron phase and scattering angles.

## Abstract

We study photoelectron angular distributions (PADs) near the ionization threshold with a newly developed Coulomb quantum-orbit strong-field approximation (CQSFA) theory. The CQSFA simulations present an excellent agreement with the result from time-dependent Schr\"odinger equation method. We show that the low-energy fan-shaped structure in the PADs corresponds to a subcycle time-resolved holographic structure and stems from the significant influence of the Coulomb potential on the phase of the forward-scattering electron trajectories, which affects different momenta and scattering angles unequally. For the first time, our work provides a direct explanation of how the fan-shaped structure is formed, based on the quantum interference of direct and forward-scattered orbits.