SGER: Improving Ruthenium Isotope Ratio Measurements: Preparing to Test for Time Dependence of Fundamental Constants

SGER：改进钌同位素比测量：准备测试基本常数的时间依赖性

• 批准号: 0307352
• 负责人: Judith Hannah
• 金额: $ 2.96万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-04-01 至 2004-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0307352&HistoricalAwards=false
• 关键词: SGER; Improving; Ruthenium; Isotope; Ratio

HannahEAR-0307352The possibility of time dependence of fundamental constants, including the weak interaction constant, has been long debated in the physics community. One approach to documenting time dependence is to seek variations in the decay constants for radioactive elements. The mineral molybdenite (MoS2), which takes in significant concentrations of rhenium (Re), permits measurements based on two decay constants. 187Re decays to 187Os by emitting a single b particle. 100Mo decays to 100Ru by emitting two b particles. The rate of b decay is mathematically dependent on the weak interaction constant. For double b decay, that dependence is squared. We can take advantage of this difference in mathematical dependency to search for changes in the weak interaction constant over time by comparing the two decay constants. We propose to use the well-established Re-Os geochronometer to determine precisely the ages of molybdenites spanning several billion years of earth history. We will then measure the accumulation of 100Ru in those same mineral samples to determine the decay constant for 100Mo, which is currently not well known. If the weak interaction constant has varied over the last several billion years, the calculated decay constant for 100Mo will vary relative to that of 187Re. Our goal in this project is to test new laboratory methods in order to improve the precision of our 100Ru measurements. Given sufficient analytical precision, we will then extend the study to perform measurements on molybdenite samples of varied ages.

Hannahmann-0307352基本常数（包括弱相互作用常数）的时间依赖性的可能性在物理学界一直存在争议。 记录时间依赖性的一种方法是寻找放射性元素衰变常数的变化。 矿物质钼铅矿（MoS2），其中需要在显着浓度的铼（Re），允许测量的基础上，两个衰变常数。187 Re通过发射单个B粒子衰变为187 Os。 100 Mo通过发射两个B粒子衰变为100 Ru。 B衰变的速率在数学上取决于弱相互作用常数。 对于双B衰变，该依赖性是平方的。 我们可以利用这种数学依赖性的差异，通过比较两个衰变常数来寻找弱相互作用常数随时间的变化。我们建议使用完善的Re-Os地质年代计来精确确定跨越几十亿年地球历史的辉长岩的年龄。 然后，我们将测量100 Ru在这些相同的矿物样品中的积累，以确定100 Mo的衰变常数，这是目前还不清楚的。 如果弱相互作用常数在过去几十亿年中发生了变化，那么100 Mo的衰变常数将相对于187 Re有所变化。 我们在这个项目中的目标是测试新的实验室方法，以提高我们100 Ru测量的精度。 如果有足够的分析精度，我们将扩展研究，对不同年龄的镁铝石样品进行测量。