Generation of 'Super-Ponderomotive' Electrons due to a non-Wakefield interaction between a Laser Pulse and a Longitudinal Electric Field

TL;DR

This paper demonstrates a novel non-wakefield interaction mechanism between a laser pulse and a longitudinal electric field that can generate electrons with momenta exceeding the traditional free electron limit, supported by 2D PIC simulations.

Contribution

It introduces a new two-stage 'anti-dephasing' mechanism for producing super-ponderomotive electrons in laser-plasma interactions.

Findings

Electrons can surpass the free electron momentum limit.

The 'anti-dephasing' mechanism significantly influences electron acceleration.

Simulations confirm the mechanism's impact on electron energy.

Abstract

It is shown that electrons with momenta exceeding the `free electron' limit of $m_eca_0^2/2$ can be produced when a laser pulse and a longitudinal electric field interact with an electron via a non-wakefield mechanism. The mechanism consists of two stages: the reduction of the electron dephasing rate $\gamma-p_x/m_ec$ by an accelerating region of electric field and electron acceleration by the laser via the Lorentz force. This mechanism can, in principle, produce electrons that have longtudinal momenta that is a significant multiple of $m_eca_0^2/2$. 2D PIC simulations of a relatively simple laser-plasma interaction indicate that the generation of super-ponderomotive electrons is strongly affected by this `anti-dephasing' mechanism.