离焦量对空气中激光诱导铜等离子体光谱特性的影响

Influence of Defocusing Distance on the Laser-Induced Cu Plasma in Air

利用Nd:YAG脉冲激光在空气中烧蚀金属Cu靶,获得等离子体光谱;采用改变离焦量的方法,研究了离焦量的变化对谱线结构及谱线强度的影响;分析了离焦量分别为1 mm、0 mm和—2 mm时,沿靶面法线方向不同空间距离处电子温度的演化规律;并对等离子体光谱的特性和产生机制进行了讨论.结果表明,谱线结构、谱线强度和等离子体的电子温度都与离焦量的变化密切相关,聚焦点在—2 mm处Cu I谱线相对强度出现峰值,电子温度数值最大;聚焦点在—0.5 mm和—1.0 mm附近谱线相对强度遽然降低的现象是由于等离子体的屏蔽效应造成的.

The plasma spectra have been measured with a pulsed Nd. YAG laser which induced plasma from a metal copper target. Varying defocusing distance the influence of the relative intensity and spectral structure in various laser focusing distances from the target is studied. Space distribution characters of electron temperature are measured with defocusing distances at 1 mm before target,0 mm on the sample surface,and 2 mm back the sample. At the same time we analyze the characteristics and mechanism of the plasma spectra. The results show that the spectral structure, spectral intensity and electron temperature prominently depend on the defocusing distances. The focusing position 2 mm back the sample surface can be found that produces the maximum of copper atom spectra intensity and the electron temperature maximum. And the phenomena that the spectral intensities fall off at the the focusing position 0. 5 mm and 1.0 mm below the sample surface can be interpreted by the shielding effect.