FEL-based study of intervalley elastic scattering of donor excited states in multivalley semiconductors.

FEL-based optical pump-probe technique is usually applied for study of highly non-equilibrium electrons in semiconductors and in particularly for the relaxation of donor or acceptor bound excited states. Here we are focused on intervalley elastic scattering that is typical for donors in silicon crystal. As shown such process results in an additional feature in a pump-probe response that has been ignored so far in the interpretation of data obtained using FELIX and FELBE free electron lasers. On the other hand the knowledge on the elastic intervalley scattering is also important from physical point of view.