Analysis of a high-concentration copper in metal alloys by emission spectroscopy of a laser-produced plasma in air at atmospheric pressure

In order to investigate the possibility of analysis of a high concentration (4.5–90%) of copper in metal alloy samples (Al alloys and brass) with a laser microprobe analyzer in air at atmospheric pressure, the emission characteristics of plasmas produced by a Q-switched Nd:YAG laser over a laser energy range of 30–90 mJ (irradiance: 9.5×109–2.9×1010 W cm−2) were studied using time-resolved spectroscopy. The experimental results showed that the effect of self-absorption can be reduced by increasing the laser pulse energy. The results of time-resolved spectroscopy of laser-induced plasmas indicated that self-absorption is predominant during short time-periods (t<0.4 μs) after the laser pulse, and a time delay is effective for the reduction of self-absorption. At a high laser energy of 90 mJ, a linear calibration curve with a slope near unity was obtained for the analysis of copper in the concentration range from 4.5 to 20% with a gate width of 0.4 μs at a delay time of 0.4 μs after the laser pulse.