利用Nd∶YAG纳秒激光脉冲烧蚀硅产生等离子体光谱,通过改变聚焦透镜到样品表面的距离,研究硅等离子体光谱中原子谱线强度和离子谱线强度的变化,主要讨论的谱线为Si(I) 390.55 nm和Si(II) 385.60 nm。结果表明:Si(I)谱线强度和Si(II)谱线强度的变化依赖于透镜到样品表面的距离,随着透镜到样品表面的距离的增大,谱线强度先升高后降低;当样品表面远离焦点时,Si(I)谱线强度高于Si(II)谱线强度;当样品表面接近焦点时,Si(II)谱线强度高于Si(I)谱线强度;激光能量密度升高可使产生的等离子体中更多的原子电离成离子,使得离子谱线强度升高;改变透镜到样品表面的距离能优化激光诱导击穿光谱的辐射强度,同时能优化离子谱线强度与原子谱线强度的比值。

A Nd∶YAG (yttrium aluminum garnet) nanosecond laser pulse is used in this study to ablate silicon for producing plasma spectroscopy. Further, the changes of the atomic and ionic spectral lines in the silicon plasma spectra are studied by changing the distance from focusing lens to sample surface (LTSD). The main lines discussed are Si(I) 390.55 nm and Si(II) 385.60 nm. The results show that the changes in the spectral intensities of Si(I) and Si(II) are strongly dependent on the LTSD. The spectral intensity initially increases and subsequently decreases with an increase in LTSD. In addition, the intensity of the Si(I) line is higher than that of the Si(II) line when the sample surface is located far from the focal point. In contrast, the intensity of the Si(II) line is higher than that of the Si(I) line when the sample surface is located near the focal point. At a high laser energy, more atoms in the produced plasma are ionized into ions, and the ionic line intensity is observed to increase accordingly. Changing the LTSD can optimize the spectral intensity of laser-induced breakdown spectroscopy and the ratio of ionic and atomic lines.