激光诱导金属等离子体中的自吸效应研究

为了减小激光诱导等离子体中光谱线自吸收对分析结果的影响，提高发射光谱的谱线质量，实验利用组合式多功能光栅光谱仪和CCD探测器等组成的光谱分析系统记录光谱信息，采用平面反射镜装置对激光等离子体进行约束，比较了不同实验条件下光谱线的线型演化过程，并且通过测量等离子体的温度、电子密度以及样品蒸发量给出了合理解释。实验结果表明，当采用合适的平面反射镜装置约束激光等离子体时，等离子体的轴向温度有所升高，径向温度分布趋于均匀;等离子体的电子密度有较大幅度的提高;然而，样品蒸发量却有比较明显的减小。这几个方面的原因能够有效地降低光谱线的自吸收程度。由此可见，利用平面反射镜装置优化实验条件以后，可以有效减小激光诱导等离子体发射光谱的自吸收效应，在常量元素的定量分析中，允许选择灵敏谱线作为分析线，这为提高激光诱导击穿光谱技术的精确测量奠定了基础。

Study of Self-Absorption Effect on Laser-Induced Metal Plasma

In order to reduce the effect of the spectral line self-absorption on the analysis result in the laser induced plasma and enhance the qualities of spectrum, the spectral information was recorded by the spectral analysis system consisting of a modular multifunctional grating spectrometer and a CCD detector etc., and the electron temperature and electron density of the plasma were measured with the spectroscopic methods. A plane mirror device was used to constraint the laser plasma, and a reasonable explanation was got through comparing the linear evolution under different experimental conditions and measuring the temperature, electronic density and sample evaporation. The result shows that when an appropriate plane mirror device was used to constraint the laser plasma, the axial temperature of the plasma increased and the radial distribution of the plasma becomes uniform; the electron density increased dramatically; however, obviously sample evaporation decreased, which may be the reasons for being able to effectively reduce the level of self-absorption spectral lines. Therefore, the plane mirror device could reduce the self-absorption effect in the laser-induced plasma. This makes it possible to choose a sensitive line that acts as analysis line in the quantitative analysis of the major elements. In other words, this promotes the measurement precision in the laser-induced breakdown spectroscopy.