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增强激光诱导等离子体的发射光谱强度,对于精确测量微弱光谱信号,改进待测材料中低含量元素的探测灵敏度意义重要。首先对金属样品加热升温,并且在一定温度时利用波长为1 064 nm的Nd:YAG纳秒脉冲激光烧蚀样品,激发产生等离子体,测量了不同样品温度条件下等离子体的发射光谱强度和信噪比。结果表明,采用的激光能量为200 m J时,随着样品温度的升高,等离子体辐射会逐渐增强,并且在温度为150℃时达到最大。计算表明,样品中分析元素Mo、Cr、Ni和Mn在温度为150℃时的光谱线强度比室温条件下的分别提高了54.56%,72.43%,70.29%和54.01%,光谱信噪比分别增大了37.44%,40.74%,38.6%和37.06%。实验还通过观察等离子体的照片,测量等离子体的温度、电子密度和样品蒸发量,讨论了激光诱导金属等离子体辐射增强的原因。可见,升高样品温度是改善激光等离子体光谱质量的一种有效手段。
Increasing the intensity of the laser-induced plasma emission spectrum is important for accurately measuring weak spectral signals and improving the detection sensitivity of low content elements in the material under test. Firstly, the metal sample is heated and heated, and at a certain temperature, the Nd: YAG nanosecond pulsed laser with a wavelength of 1 064 nm is used to ablate the sample to excite the plasma, and the intensity of the emission spectrum of the plasma under different sample temperatures is measured Noise ratio. The results show that when the laser energy is 200 m J, the plasma radiation will gradually increase with the increase of the sample temperature and reach the maximum at the temperature of 150 ℃. The calculated results show that the spectral line intensities of Mo, Cr, Ni and Mn in samples are increased by 54.56%, 72.43%, 70.29% and 54.01% respectively at room temperature under the condition of 150 ℃. The spectral signal-to-noise ratio Big 37.44%, 40.74%, 38.6% and 37.06%. The experiment also discussed the reason of laser-induced enhancement of metal-plasmon radiation by observing plasma photos, measuring plasma temperature, electron density and sample evaporation. It can be seen that increasing the sample temperature is an effective means to improve the spectral quality of the laser plasma.