Angle-dependent interferences in electron emission accompanying stimulated Compton scattering from molecules

The high brilliance of ultrashort X-ray pulses recently generated in free electron lasers will soon open the way to the investigation of non-linear processes that still remain inaccessible due to the smallness of the corresponding cross sections. One of them is stimulated Compton scattering from molecules. In this work, we investigate stimulated Compton scattering from fixed-in-space H-2 molecules in the few-hundred eV photon energy range, where both dipole and non-dipole transitions are important. We show that the interference between dipole and non-dipole transitions leads to pronounced asymmetries in the electron angular distributions. These asymmetries strongly depend on molecular orientation, to the point that they can lead to electron emission in either the forward or the backward directions with respect to the propagation axis, or in both directions, or even in the orthogonal direction. This is in contrast with Compton scattering from free electrons or atomic targets. X-ray free electron lasers provide high brightness sources that permit the study of low-cross section phenomena, such as Compton scattering from atoms and molecules. Here, the angular distribution of electrons after stimulated Compton scattering from molecular hydrogen are simulated, revealing the influence of dipole and non-dipole transitions.