样品温度对激光诱导等离子体辐射强度的影响

Effect of sample temperature on laser-induced plasma radiation intensities

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。

Improving the intensity of laser-induced plasma emission spectrum is of great significance for enhancing the measuring accuracy of weak spectral signal and improving the detection sensitivity of low content elements in analysis material. The metal sample was heated in the first and ablated by the Nd：YAG nanosecond pulse laser with the wavelength of 1 064 nm in the air under the certain temperature. The plasma was produced. Then the line intensity and signal-to-noise ratio of spectrum were measured under the different sample temperature. The results show that, with the increase of sample temperature under the condition of laser energy for 200 mJ, plasma radiation increases and reaches the maxmum at the sample temperature of 150 ℃ Calculations show that the spectral line intensities of Mo, Cr, Ni and Mn increases by 54.56%, 72.43%, 70.29% and 54.01% respectively, and the spectral signal-to- noise ratios increases by 37.44%, 40.74%, 38.6% and 37.06% respectively compared with that of the room temperature. By observing the plasma images and measuring the temperature of the plasma, electron density and the sample evaporation, the cause of the radiation enhancement of laser-induced metal plasma was discussed. Visibly, the rise of the sample temperature is a effective method for enhancing the quality of the laser spectrum.