中文摘要：

为了改善激光诱导击穿光谱的质量,提高激光诱导击穿光谱（LIBS）技术对土壤样品中痕量元素的检测能力,研究了碳质空腔距离样品表面的高度变化对等离子体辐射强度的影响.结果表明,当有空腔约束等离子体时,其辐射强度比没有空腔约束时明显增强;随着空腔距离样品表面高度的加大,等离子体辐射强度逐渐升高,并在11 mm处达到最强,随后减弱.计算可知,样品中元素Fe,Mn,K和Ti在空腔距离靶面11 mm处的谱线强度和光谱信噪比与无空腔约束时相比,都有较大提高.最后,用Boltzmann图方法和光谱线Stark展宽法测量了等离子体的电子温度和电子密度,对等离子体辐射增强的机理进行了讨论.

英文摘要：

To improve the quality of laser-induced breakdown spectroscopy （LIBS） and the detection capability of the LIBS technique on trace elements in the soil samples, the effect of the different heights of the carbon material cavity from the target surface on the soil plasma radiation intensity was investigated. The experimental results indicate that the plasma radiation intensity is significantly enhanced by using the cavity to confine the plasma. As the height of the cavity from the sample surface increases, the plasma radiation intensity increases gradually, reaches the strongest point at 11 mm and then decreases, The theoretical results show that the spectral line intensity and spectral signal-to-noise ratio of Fe, Mn, K and Ti with cavity from the target surface 11 mm are enhanced more times than that without cavity confinement, respectively. Finally, to discuss the mechanisms of the plasma radiation, the electron temperature and electron density of plasmas were measured by the Boltzmann graph method and Stark broadening.