Modified Coulomb scattering in intense, high-frequency laser fields

We present the first accurate calculation within a recently developed nonperturbative theory for free-free transitions in intense, high-frequency laser fields, done for modified elastic scattering from a Coulomb potential. The field is assumed to be monochromatic and linearly polarized. In the high-frequency limit of the theory, the scattering takes place from a time-independent, "dressed" Coulomb potential, which contains the frequency and intensity of the field only through a parameter ${\alpha }_0$. The corresponding Schrödinger equation in integral form was solved by the close-coupling method. The cross section depends on the scattering angle $\theta$ and on two other angles defining the orientation of the initial and final momenta ${\mathrm{k}}_i$ and ${\mathrm{k}}_f$ with respect to the electric field. Large deviations from the Rutherford cross section are found in the nonperturbative regime. At small angles θ the deviations appear in the form of characteristic Coulomb interference oscillations, while in backward scattering this pattern is distorted in a way markedly dependent on the orientation of the momenta with respect to the electric field. An unexpected rotation invariance of the cross section around ${\mathrm{k}}_i$ was found for certain "magic" scattering angles $\theta$.