激光诱导Al等离子体中电子密度和温度的实验研究

激光烧蚀等离子体在微量元素分析方面有着重要的应用背景，而缓冲气体的种类及压力对激光等离子体的特性有重要影响。报道了以氦气、氩气、氮气和空气作为缓冲气体，实验测定了不同气压下Nd：YAG激光烧蚀Al靶产生的等离子体中的时间分辨发射光谱，利用发射谱线的Stark展宽和相对强度计算了等离子体中的电子密度和温度，得到了在不同缓冲气体中激光诱导Al等离子体的电子密度随延时、气压的演化规律，同时得到了电子温度的时间演化特性。实验结果表明，电子密度的数量级约为10^17cm^-3，电子温度测量值约为10000K，二者都是在激光脉冲后随时间快速衰减，直到4μs以后达到一个较低的水平并缓慢变化，其中以氩气作为缓冲气体时等离子体中的电子密度最大。

Experimental Investigation on the Electron Density and Electron Temperature of Laser-Induced Al Plasmas

The laser-induced plasma plays an important role in the trace element analysis. The properties of plasma are dependent on the kinds and pressure of buffer gas. With He, Ar, N2, Air as buffer gases respectively, the time-resolved emission spectra of laser induced Al plasmas at different pressure are measured. The electron density and electron temperature of Nd∶YAG laser-induced Al plasma are calculated by the measured relative emission-line intensity and Stark broadening. The dependence of electron density on the time delay, kinds and pressure of the buffer gas are studied. The time evolution property of the electron temperature is also obtained. The experimental results show that the electron density and the electron temperature in laser induced Al plasmas are the order of 1017 cm-3 and 10000 K respectively. They are both decayed rapidly with the time delay from the laser pulse off and then changed slowly after 4 μs. Among several of buffer gases, the electron density is the largest in Ar gas.