激光共振电离过程中铅同位素歧视效应研究  

Laser-Induced Isotopic Discrimination Effect in Laser Resonance Ionization Process of Lead Atom

作　　者：王新顺[1] 李颖[1] 戴琳[1] 郑荣儿[1] 

机构地区：[1]中国海洋大学光学光电子实验室,山东青岛266071

出　　处：《光谱学与光谱分析》2008年第7期1454-1458,共5页Spectroscopy and Spectral Analysis

基　　金：国家"863"项目(2006AA09Z243);山东省自然科学基金项目(Y2006A26)资助

摘　　要：以速率方程为基础,通过数值模拟方法,对Pb的激光共振电离通道:"6s26p23P0—6s26p7s3P10—电离"的激光诱导同位素歧视效应进行了研究,以探讨减小激光诱导歧视效应,准确测定Pb同位素比值的有效途径。通过考虑激光线型、原子吸收谱线线型、同位素位移及同位素超精细结构等因素的影响,对速率方程进行近似。在近似的速率方程基础上,以"1+1"激光共振电离过程为例,进而探讨激光峰值功率密度、带宽和中心波长对Pb的同位素歧视效应的影响。研究结果表明,利用最佳波长法,可基本消除同位素歧视效应的影响;提高激发光光强可使Pb同位素饱和电离,从而消除同位素歧视效应的影响;采用宽带激光激发,可减小同位素歧视效应的影响。Isotope ratio measurements have been increasingly used in geochemistry, geochronology, cosmos chemistry and environmental science. Precise and accurate isotope ratio measurements are an important task in many applications such as the determination of isotope variations in geological and cosmic samples. Due to its high sensitivity, high ionization efficiency and high element selectivity, laser resonance ionization spectroscopy has nowadays become one of the key techniques, including isotope ratio measurements and trace amount analyses. Because of the isotope shifts and hyperfine structure, there is laser-induced isotopic discrimination effect in the process of laser resonance ionization. The different isotope ionization efficiency can affect precise and accurate measurement of isotope ratios. In the present paper, the dependences of the laser-induced isotopic discrimination effect on some of the laser parameters were studied by theoretical methods. Based on the numerical simulation of the population rate equations, laser-induced isotopic discrimination effect of lead isotopes was studied, by calculating laser resonance ionization transition ＂6s^2 6p^23 P0-6s^2 6p7s^3 P1^0→ionization＂. The population rate equations was approximated considering some factors which affect the probability of laser resonance transition such as spectral lines width of laser and atom, isotope shifts and hyperfine structure. According to the approximated population rate equations, ＂1 ＋ 1＂ laser resonant ionization process was employed to calculate the ionization probability of lead isotopes by means of computer simulation. The dependences of laser-induced isotopic discrimination effect on the laser parameters, such as laser central wavelength, bandwidth and intensity were investigated. The calculated results show that the laser-induced isotopic discrimination effect of lead isotopes could be almost eliminated by operating at optimized wavelength and could be lessened by using wide band laser. Saturated ionization of lead isotop

关 键 词：铅同位素 激光共振电离 激光诱导同位素歧视效应 

分 类 号：O433.5[机械工程—光学工程]