Electron scattering in intense laser fields

Abstract

The authors report quantitative measurements of multiphoton free-free (FF) transitions in a controlled three-beam experiment: electrons elastically scattered from argon in the presence of a CO₂ laser pulse having an average flux density between 10⁶ and 10⁸ W cm^-2. They present FF spectra for four incident electron energies, two scattering angles, and two directions of the laser polarisation vector. Electrons that have changed their kinetic energy by as many as eleven photons have been detected. From the spectra the absolute average flux density of the laser pulse was determined and the validity of the sum rule examined. Both results are indirect verifications of the theory.