Stimulated Raman scattering (SRS) in plasma in a non-eigenmode regime is studied theoretically and numerically. Different from normal SRS with the eigen electrostatic mode excited, the non-eigenmode SRS is developed at plasma density $n_{e}>0.25n_{c}$ when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency $\unicode[STIX]{x1D714}_{0}/2$ , which is no longer the eigenmode of electron plasma wave $\unicode[STIX]{x1D714}_{pe}$ . Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super-hot electrons are produced by the non-eigen electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than $10^{15}~\text{W}/\text{cm}^{2}$ .

中文翻译：

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非本征模式下的受激拉曼散射

在理论上和数值上研究了非本征模式等离子体中的受激拉曼散射 (SRS)。与本征静电模式激发的普通 SRS 不同，非本征模式 SRS 是在等离子体密度下发展的 $n_{e}>0.25n_{c}$ 当激光振幅大于某个阈值时。为了满足频率和波数的相位匹配条件，激发的静电模式在入射光频率的一半左右具有恒定的频率 $\unicode[STIX]{x1D714}_{0}/2$ ，不再是电子等离子波的本征模式 $\unicode[STIX]{x1D714}_{pe}$ . 散射光和静电波都被困在等离子体中，它们的群速度为零。超热电子是由非本征静电波产生的。我们的理论模型通过细胞内粒子模拟得到验证。只要激光强度高于 $10^{15}~\text{W}/\text{cm}^{2}$ .