Relativistic Raman Instability Shifted by Half-Plasma Frequency
Authors: G. Shvets, N. Fisch, J. Rax
A new nonlinear Raman instability in underdense plasma is investigated theoretically. Unlike the usual linear Raman instabilities which grow exponentially in time, this instability takes a finite amount of time to diverge. The explosion time t° depends on the initial level of the perturbation. A general set of equations for spatio-temporal evolution of the forward nonlinear Raman scattering is derived and its temporal evolution is studied in detail. This new instablity results in the generation of forward Raman radiation shifted by half the plasma frequency for laser intensities of order or exceeding 1018W/cm2, someting that has been recently observe