Energy-exchange characteristics in ordinary and nonlinear Compton scattering

Free-electron-photon interaction, if it occurs inside an intense laser fiel d, will be dominated by nonlinear Compton scattering (NLCS), which is quite different from the ordinary Compton scattering. The difference can be, for example, in the number of photons involved in one interaction. In this pap er, by both analytical and numerical methods, we will explore in detail the ir characteristics from the viewpoint of energy exchange in the interaction . Based upon the well-displayed results, we are able to, furthermore, revea l some phenomena underlying NLCS and investigate the corresponding physical implications, such as the threshold effects in NLCS. That is, when Q = eE/ (ln,wc)>0.1, the: low-order NLCS will be depressed while the high orders wi ll be excited. And when Q > 10 the high-order NLCS process will become domi nant in the electron-photon interaction. As for Q > 100, the extra-high-ord er NLCS will be so strongly excited that the electron dynamics will enter a new regime. Also, we can mal;make use of the obtained results to explain q ualitatively the NLCS experiment by Bula el nl. [S1050-2947(99)02106].