Observation of electron trapping and phase-area displacement in the interaction between an electron beam and two counter-propagating laser beams

We report the observation of synchronous energy exchange between nonrelativistic electrons and the ponderomotive (beat) force of two counterpropagating, intense, pulsed CO2 laser beams, operating at different frequencies in a stimulated Compton scattering scheme. The interaction takes place in the nonlinear (trapping) regime, and its physics is the same as in laser accelerators and efficiency-enhanced free-electron lasers with long wigglers. Two different mechanisms of enhanced energy transfer were observed electron trapping and phase-area displacement.