Electron-energy bunching in laser-driven soft recollisions

TL;DR

This paper introduces the concept of soft recollisions in laser-matter interactions, showing they cause universal low-energy peaks in photo-electron spectra independent of the binding potential.

Contribution

It presents an analytical demonstration of soft recollisions leading to energy bunching and low-energy peak formation, expanding understanding of laser-driven electron dynamics.

Findings

Universal low-energy peak sequence in electron yield

Peak sequence occurs below 0.2 times ponderomotive energy

Soft recollisions differ from head-on collisions in electron recollision dynamics

Abstract

We introduce soft recollisions in laser-matter interaction. They are characterized by the electron missing the ion upon recollision in contrast to the well-known head-on collisions responsible for high-harmonic generation or above-threshold ionization. We demonstrate analytically that soft recollisions can cause a bunching of photo-electron energies through which a series of low-energy peaks emerges in the electron yield along the laser polarization axis. This peak sequence is universal, it does not depend on the binding potential, and is found below an excess energy of one fifth of the ponderomotive energy.