High-frequency collective modes in plasma with strongly anisotropic velocity distribution of photoelectrons formed by multiphoton or above-threshold ionization of gas atoms are studied. In the case of multiphoton ionization, along with the usual electromagnetic wave, there are two additional modes. In the region of large wavelengths, the higher-frequency mode is similar to the electron Langmuir wave. Its group velocity is mainly determined by the average photoelectron velocity, and Cherenkov damping is due to small velocity dispersion of photoelectron distribution. In the region of short waves, but with a small Cherenkov damping, the group and phase velocities of this wave are close to the average electron velocity. The second mode, which has lower frequency, in the region of wavelengths smaller than the ratio of average electron velocity to the plasma frequency, corresponds to quasi-potential wave. Its dispersion law is close to the linear one. In contrast, in the region of lar...

中文翻译：

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稀有气体多光子电离形成的等离子体的集体模式

研究了由多光子或高于阈值的气体原子电离形成的光电子具有强各向异性速度分布的等离子体中的高频集体模式。在多光子电离的情况下，与通常的电磁波一起，存在两种附加模式。在大波长区域，高频模式类似于电子朗缪尔波。它的群速度主要由平均光电子速度决定，而契伦科夫阻尼是由于光电子分布的速度分散小所致。在短波区域，但在Cherenkov阻尼较小的情况下，该波的群速度和相速度接近平均电子速度。频率较低的第二种模式 在小于平均电子速度与等离子体频率之比的波长区域中，对应于准势波。它的色散定律接近线性定律。相反，在较大的地区