Modelling radiation emission in the transition from the classical to the quantum regime

TL;DR

This paper derives a corrected emissivity formula for radiation emission during the transition from classical to quantum regimes, validating it against QED approaches and identifying quantum signatures in nonlinear Thomson scattering.

Contribution

It introduces a generalized emissivity formula accounting for recoil effects, bridging classical and quantum models, and validates it through comparison with QED methods.

Findings

The corrected formula aligns with QED results in applicable regimes.

Quantum signatures are identifiable in nonlinear Thomson scattering.

Good agreement between the new method and QED probabilistic approaches.

Abstract

An emissivity formula is derived using the generalised Fermi-Weizacker-Williams method of virtual photons which accounts for the recoil the charged particle experiences as it emits radiation. It is found that through this derivation the formula obtained by Sokolov et al using QED perturbation theory is recovered. The corrected emissivity formula is applied to nonlinear Thomson scattering scenarios in the transition from the classical to the quantum regime, for small values of the nonlinear quantum parameter \chi. Good agreement is found between this method and a QED probabilistic approach for scenarios where both are valid. In addition, signatures of the quantum corrections are identified and explored.