New Model of Raman Spectra in Laser-Produced Plasma

Abstract

Observations of Raman scattering in laser-produced plasma can be explained by incoherent Thomson scattering, with a greatly enhanced "plasma line." Reversed-slope velocity distributions in the underdense region are produced by hot-electron pulses originating near the quarter-critical surface ($\frac{n_c}{4}$). The model explains the two gaps in the Raman spectrum, the correlation of scattering "onset" with that of instability at $\frac{n_c}{4}$, the "scintillation" in frequency and time, and the weak angular variation. An "upscattered" frequency band is predicted and has been verified by experiment.