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

包括弱相互作用常数在内的基本常数的时间依赖性的可能性，在物理界已经争论了很长时间。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。辉钼矿（MoS2）含有大量的铼（Re），可以根据两个衰变常数进行测量。187Re通过释放一个b粒子衰变成187Os。100Mo通过释放两个b粒子衰变成100Ru。b的衰变速率在数学上依赖于弱相互作用常数。对于双b衰变，这种相关性是平方的。我们可以利用数学依赖性的这种差异，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。我们建议使用成熟的Re-Os地球计时器来精确确定地球几十亿年历史中辉钼矿的年龄。然后，我们将测量100Ru在这些矿物样品中的积累，以确定100Mo的衰变常数，这是目前尚不清楚的。如果弱相互作用常数在过去几十亿年中发生了变化，那么100Mo的计算衰变常数将相对于187Re发生变化。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100Ru测量的精度。考虑到足够的分析精度，我们将扩展研究，对不同年龄的辉钼矿样品进行测量。

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.