Effect of negative ions on stimulated Raman scattering in a plasma

Abstract

In the linear theory of stimulated Raman scattering based on the three-fluid model, the effect of negative ions is reflected in the growth rate through simple functions of P (the relative fraction of negative ions in the number of negatively charged particles in a plasma). The Raman instability is weakened by negative ions, when the pump intensity is well above the threshold, while it is strengthened close to the threshold.

Detuning effect of negative ions on ion-acoustic-decay instabilities of electromagnetic waves

“…Thus, in stimulated scattering instabilities, negative ions can raise or lower the instability threshold and the growth rate by affecting plasma waves, the ponderomotive force, and the nonlinear current. [2][3][4][5][6] For filamentation instabilities, a critical level of the pump intensity is reported, where the growth rate dependence on negative ions shows a qualitative change. 7 On the other hand, for parametric instabilities occurring at the critical density layer of the plasma, the conspicuous effect of negative ions is the detuning of the sideband frequency outside the resonance range, rather than the changing of the threshold or the growth rate.…”

Phenomena in gases and plasmas with negative ions

“…Неустойчивость тангенциального разрыва (Кельвина -Гельмгольца) в плазме с отри-цательными ионами исследовалась в [108], распро-странение электромагнитных волн в такой плазме -в [109][110][111][112]. Изучено также влияние отрицатель-ных ионов на стимулированное бриллюэновское [113,114] и рамановское [115] рассеяние электро-магнитных волн в плазме. Не только величина, но и знак перечисленных эффектов зависят от конкрет-ных условий.…”

Effect of negative ions on filamentation instability in collisionless three-fluid theory of plasmas with cold ion species

“…14 And in the stimulated Raman scattering, the instability may be enhanced by negative ions near the threshold, while the weakening effect may be seen at intensities well above the threshold. 15 In this work we address another parametric instability, i.e., the filamentation instability, where an intense electromagnetic wave interacts parametrically with a nonoscillating plasma density perturbation developed across its propagation direction. Under proper phase matching conditions, the density perturbation is increased by radiation pressure force formed by interference of incident and scattered waves.…”