【作者】 汪越；

【导师】 吴伟明； 姜山；

【作者基本信息】 广西大学 ， 理论物理， 2005， 硕士

【摘要】 ³⁶Cl是一种长寿命放射性核素,它广泛存在于大气圈和岩石圈中。通过测定灰岩样品中的³⁶Cl含量,可以计算灰岩的侵蚀速率以及暴露年龄。但灰岩中的³⁶Cl含量很低,目前,加速器质谱（ANS）是测量灰岩中³⁶Cl的唯一有效的方法。研究不同环境下的侵蚀速率对科学和经济来说,都是很重要的。此研究方法可以推广到地壳的隆升和断代等,以及拓展加速器质谱（AMS）在环境样品中的应用。 灰岩中的³⁶Cl主要来源于以下几种反应: ⁴⁰Ca（n,2n3p）³⁶Cl;³⁵Cl（n,γ）³⁶Cl;⁴⁰Ca（μ,α）³⁶Cl。 在灰岩顶部数米范围内,前两种反应占主导地位。随着深度的增加,由⁴⁰Ca的负μ介子俘获反应产生的³⁶Cl的贡献会相应地增大。 地表灰岩中宇宙成因核素的浓度（N）要受到侵蚀（ε）的限制。对于侵蚀速率恒定的简单情况来说,宇宙成因核素³⁶Cl在灰岩表面中的浓度（N）由下列方程给出: 式中:N为经过暴露时间t时、灰岩表面以下深度z（米）处宇宙成因核素³⁶Cl的浓度（原子/克）,λ为³⁶Cl的衰变常数(年^-1),ε为侵蚀速率（米/年）,P（z）为³⁶Cl的总产生率（原子/（克·年））。据此,我们得到北京地区灰岩表面的侵蚀速率为（1.33±0.28）×10^-5米/年。 本论文研究内容主要包括以下五个部分:第一部分是侵蚀概述;第二部分是³⁶Cl的来源及利用³⁶Cl进行侵蚀速率计算的定量模型;第三部分是灰岩样品的采集和待测样品AgCl的制备,在此过程中主要是降低³⁶S的含量以减小在³⁶Cl测量过程中的干扰。同时,在AgCl样品制备的过程中需加适量的氯化物（NaCl）载体;第四部分是³⁶Cl的AMS测定。此工作是在中国原子能院串列加速器和日本Tsukuba大学的加速器上完成的;第五部分是结果与讨论。更多还原

【Abstract】 ~36Cl, the long-lived radioactive nuclide distributes abroad in atmosphere and lithosphere. By measuring the concentration of ~36C1 in limestone, the erosion rates and exposure ages of limestone can be determined. In recent years, Accelerator Mass Spectrometry (AMS) is the only effective tool to measure ~36C1 in limestone. It is very significant for science and economy to study the erosion rate of different circumstance .This technology and method can be extended to study the flourishing of the earth’s crust and to judge the age of something and even can help to extend the applications of AMS in circumstance science.In the case of ~36C1 in limestone, the most important reactions are the followings:~40Ca(n, 2n3p)~36Cl; ~ 35Cl(n, γ)~36C1; ~40Ca(μ, α)~36ClIn the top meter of the limestone, the reactions of ~40Ca(n,2n3p)~36Cl and ~35Cl(n, γ )~36C1 are dominant. Following the depth increases, the contribution from slow μ capture by ~40Ca becomes progressively more important.As for as a radioactive nuclide ~36C1, its concentration in limestone can be expressed reasonably by the equation:Where, P-the total production of ~36C1; N-the concentration of ~36C1; λ -the decay constant of 36C1; z-the depth of sample; t- exposure age; e- erosion rate. According to this equation , the erosion rate of limestone in Beijing City has been calculated and the erosion rate is (1.33 ± 0.28) × 10~-5m.a~-1.The article is composed of five sections. First, the review about erosion rate. Second, the origin of ~36C1 and the theory about calculation of erosion rate. Third, collecting of limestone samples and making of AgCl. For the AgCl sample preparation, the carrier of Cl is added to the limestone solution and a chemical procedure is used to reduce the abundance of sulfur. Fourth, AMS measurement, it is completed at CIAE-AMS system and Tsukuba university AMS system in Japanese. Fifth, conclusions and discussions.The author mainly do the following work: grasping the mechanism by which the cosmogenic nuclide of chlorine-36 produce, preparing and making the sample of AgCl, as a participant of AMS measurement, last but not least, searching for a reasonable math model and calculating erosion rate.更多还原