采用波长532 nm激光(脉宽为8 ns)诱导激发铜合金等离子体光谱, 研究了激光能量分别为100, 80, 60和40 mJ时, 常压下谱线(CuⅠ 324.754 nm)自吸收现象; 在激光能量为100和40 mJ的条件下, 研究了低环境压力对铜合金等离子体元素发射谱线自吸收现象和谱线特性的影响。 结果表明: 常压下谱线(CuⅠ 324.754 nm)存在严重的自吸收现象, 自吸收程度随激光能量减小而降低。 适度降低环境压强, 谱线的自吸收程度大大降低, 谱线的信背比增大, 且在一定的低气压条件下, 自吸收现象可以基本消除。 在5.0×104 Pa气压下, 两种能量下谱线的信背比均达到最大值, 分别为8.90和8.66, 相对于常压分别增大了11.23和12.62倍, 此时谱线强度的相对标准偏差分别为2.9%和1.3%; 两种能量下等离子体元素发射谱线的线宽随着气压的下降迅速减小, 当气压为5.0×104 Pa时, 等离子体元素发射谱线的线宽分别为0.08和0.06 nm, 是常压下线宽的19%和20%。 研究表明: 低压环境能明显提高光谱分析的灵敏度和精密度, 使得在分析较高含量元素时允许选择灵敏谱线, 为采用LIBS技术准确测定高含量元素提供了有效方法。

The self-absorption of copper alloy plasma spectrum was studied by using 532 nm laser (pulse width of 8 ns) under the laser energy of 100, 80, 60 and 40 mJ. The effects at low ambient pressure on the self-absorption and spectral characteristics of copper alloy plasma were studied under the laser energy of 100 and 40 mJ. The research showed that the characteristic line (Cu Ⅰ 324.754 nm) has a serious self-absorption at standard atmospheric pressure, and the degree of self-absorption reduced with the decrease of laser energy. By reducing the environmental pressure properly, the degree of self-absorption greatly reduced, the SBR(Signal-to-Back Ratio) increased, and the self-absorption phenomenone liminated under a certain low pressure. Under the pressure of 5.0×104 Pa, the SBR under two laser energy reached its maximum value, which were 8.90 and 8.66 respectively, 11.23 and 12.62 times higher than the SBR at normal pressure, and the RSD (Relative Standard Deviation) were 2.9%, 1.3% at present. The spectral widths of two laser energy decreased rapidly with the decrease of ambient pressure. The spectral widths were 0.08 and 0.06 nm at the pressure of 5.0×104 Pa, which were 19% and 20% with the value of widths under normal pressurere spectively. The results showed that sensitivity and precision in spectral analysis can be significantly improved under low-pressure. It indicates that to select the element sensitive spectral line as analysis line is possible when analyzing higher content elements, and provides an effective method for the determination of high content elements in material accurately by LIBS.