A short focused laser pulse can generate a hot plasma, which expands then contracts and can eject a hot jet, the speed and direction of which is sensitive to the details of the plasma kernel. The coupling of thermal and chemical nonequilibrium plasma mechanisms with this hydrodynamic development is assessed with detailed simulations of a two-temperature, three-species plasma model. Time scales for electron recombination, thermal relaxation, and diffusion are compared to that of the plasma expansion to anticipate conditions in which these mechanisms might affect the vorticity generation that leads to the ultimate flow pattern. The effect of these mechanisms are analyzed through comparison with corresponding inert-gas and equilibrium models. Thermal-nonequilibrium effects are found to be weak due to rapid relaxation of the heavy-particle and electronic temperatures. In contrast, chemical equilibration occurs at a rate comparable to the expansion and thereby enhance both it and subsequent hydrodynamic mechanisms as the energy stored in ion formation during the preceding breakdown is released by electron recombination. Thermal conduction, enhanced by high-temperature free electrons, weakens the ejection.

中文翻译：

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介导由激光引起的光击穿引起的流动的热效应

短聚焦激光脉冲可以产生热等离子体，该等离子体膨胀然后收缩并可以喷射出热射流，其速度和方向对等离子体内核的细节很敏感。热和化学非平衡等离子体机制与这种流体动力学发展的耦合通过两个温度、三个物种的等离子体模型的详细模拟进行评估。将电子复合、热弛豫和扩散的时间尺度与等离子体膨胀的时间尺度进行比较，以预测这些机制可能影响导致最终流动模式的涡度产生的条件。通过与相应的惰性气体和平衡模型进行比较，分析了这些机制的影响。由于重粒子和电子温度的快速弛豫，发现热非平衡效应很弱。相比之下，化学平衡以与膨胀相当的速率发生，从而增强它和随后的流体力学机制，因为在先前的分解过程中储存在离子形成中的能量通过电子重组释放。由高温自由电子增强的热传导减弱了喷射。