Intensity and spin effects in electron-ion scattering in the presence of an intense laser field.

Abstract

In the 1970s the experiments of Weingartshofer et al. [Phys. Rev. Lett. 39, 269 (1977) and Phys. Rev. A 19, 2371 (1979)] have shown that the Kroll-Watson cross section for Rutherford scattering in the presence of an intense laser field is correct. In a recent paper [Phys. Rev. A 38, 2525 (1988)], by using the Volkov solution to the minimally coupled Dirac equation, we had shown that the spin of the electron would give a contribution to the heating rate of a plasma in the intense laser light. We had also developed the concept of the quasifree states of the electron from a kinematical point of view. Using these concepts, we show that the Rutherford cross section has to be modified due to the spin of the electron and also due to the high intensity of the laser radiation at the region of interaction. A new coupling (decoupling) scheme is presented separating the kinematical factors from the dynamical ones. When the electron's momenta are perpendicular to the polarization plane of the laser field (small-angle scattering), it is discovered that the net number of photons absorbed or emitted in a single scattering process is limited to less than or equal to 2. We develop a mathematical transformation in the Appendix to reduce the infinite sum over products of Bessel functions into a single finite integral so that the ratio of our cross section to that of Rutherford can easily be computed and the results are plotted for various ranges of the parameters involved.