Temporal and spatial evolution of temperature in femtosecond laser filamentation is investigated using planar Rayleigh scattering combined with optical flow algorithm, the corresponding mechanism is analyzed. The temperature increases sharply with a characteristic time of 4.53μs and reach a maximum value of 418 K within 1∼10μs, then decreases slowly to around 300 K with a characteristic time of 136μs. While the temperature first diffuses rapidly in the radial direction and then diffuses very slowly, an obvious step is observed around 2μs. The mechanism of heat transfer is the result of energy exchange between electron and heavy particles and heat conduction. Within 1 ns to 10μs, molecules obtain energy continuously due to collision with electrons, which is much larger than the energy loss due to thermal conduction, leading to rise of gas temperature and the high-speed movement of the filament edges. After 10μs, thermal conduction becomes the dominant factor, resulting gas temperature decreasing and slower movement of the filament edges.

中文翻译：

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飞秒激光丝状平面平面瑞利散射加热的时间特性

利用平面瑞利散射结合光流算法研究了飞秒激光丝化过程中温度的时空变化，并分析了相应的机理。温度以4.53μs的特征时间急剧上升，并在1〜10μs内达到418 K的最大值，然后以136μs的特征时间缓慢下降至300 K左右。尽管温度首先沿径向快速扩散，然后缓慢扩散，但在2μs左右观察到明显的阶跃。传热的机理是电子与重粒子之间的能量交换和热传导的结果。在1 ns到10μs内，分子由于与电子的碰撞而连续获得能量，该能量远大于由于热传导而产生的能量损失，导致气体温度升高和灯丝边缘的高速移动。10μs之后，热传导成为主要因素，导致气体温度下降，灯丝边缘移动变慢。