Spin dynamics in the Kapitza-Dirac effect

TL;DR

This paper presents a relativistic quantum theory of electron spin dynamics in high-intensity Kapitza-Dirac scattering, revealing spin-dependent Rabi oscillations and spin-flip transitions relevant for future X-ray laser experiments.

Contribution

It introduces a fully relativistic Dirac equation-based model to describe spin effects in high-frequency, high-intensity Kapitza-Dirac scattering, highlighting spin-dependent phenomena.

Findings

Demonstrates spin-flip transitions in Kapitza-Dirac scattering.

Shows Rabi oscillations depend on electron spin.

Predicts observable spin effects with future X-ray lasers.

Abstract

Electron spin dynamics in Kapitza-Dirac scattering from a standing laser wave of high frequency and high intensity is studied. We develop a fully relativistic quantum theory of the electron motion based on the time-dependent Dirac equation. Distinct spin dynamics, with Rabi oscillations and complete spin-flip transitions, is demonstrated for Kapitza-Dirac scattering involving three photons in a parameter regime accessible to future high-power X-ray laser sources. The Rabi frequency and, thus, the diffraction pattern is shown to depend crucially on the spin degree of freedom.