Multiphoton effects in electron-ion scattering: A limitation of the cross-section treatment

The differential cross-section for inelastic scattering of electrons in the presence of an intense laser field reported by the authors was confirmed by Ehlotzky (1988) and Krstic and Milosevic (1989), when the Kibble parameter is less than unity. However, some difficulties arise when the energy balance and heating by multiphoton process are considered. Bivona et al. (1985), (1986) have shown that the absorption coefficient, α, can be negative if v0 < vi, where v0 is the amplitude of the oscillatory velocity and vi is the particle incoming velocity. In this paper, the proper way to calculate the absorption coefficient from the cross-section treatment are presented and it is possible to show that α ≥ 0, for all values of vi. (Author)