激光大气等离子体的电子密度空间分布特性研究

利用Nd∶YAG激光器产生的1.06 μm激光束(脉冲能量为500 mJ，脉冲宽度为10 ns, 重复频率30 Hz)聚焦击穿大气形成长约为8 cm、最大直径为5 cm的激光大气等离子体柱，用光谱测量的方法，分别沿平行于激光束方向和垂直于激光束方向探测该等离子体柱的空间分辨光谱，并由此反演得出电子密度空间分布特性。实验结果表明，激光大气等离子体中各种离子和电子呈橄榄形分布，沿激光束方向不对称，而垂直激光束方向对称分布，最大电子密度为1018 cm-3。文章还探讨了激光大气等离子体中处在不同状态的各种原子、分子和离子在空间的分布特性，为进一步揭示激光大气等离子体的微观空间分布规律提供了实验依据。

Study on the Electron Density Distribution of Laser-Induced Air Plasmas

An 1. 06 microm Nd : YAG laser beam (energy: -500 mJ/pulse, pulse width: 10 ns, repetition rate: 30 Hz) was focused by a conical lens, and a column of laser-induced air plasmas (LIAP) came into being. The LIAP column, about 8 cm of long and 5 cm in maximal diameter, was studied by spectra measurement. The spectra of the LIAP column at different position were measured in the directions both perpendicular and parallel to the laser propagation respectively. From these data, the electron densities of the LIAP were evaluated. The experimental results indicate that the LIAP formed in an olivary shape, i. e. , symmetrical in the vertical direction but unsymmetrical in the horizontal direction, and the maximal electron density is about 10(18) cm(-3). The spatial distributions of atoms, molecules and ions in different states in the LIAP were also discussed, and provide clues for discovering the microstructure of LIAP.