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

HannahEAR-0307352包括弱相互作用常数在内的基本常数随时间变化的可能性在物理学界争论已久。记录时间依赖关系的一种方法是寻找放射性元素衰变常数的变化。矿物辉钼矿(MoS2)可以吸收大量的Re(Re)，可以根据两个衰变常数进行测量。187Re通过发射单个b粒子衰变到187Os。100Mo通过发射两个b粒子衰变到100Ru。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，这种依赖是平方的。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。我们建议使用久负盛名的Re-Os地质计时仪来精确测定辉钼矿的年龄，时间跨度跨越地球数十亿年的历史。然后我们将测量100Ru在这些相同矿物样品中的累积，以确定100Mo的衰减常数，这一点目前还不是很清楚。如果弱相互作用常数在过去的几十亿年中发生了变化，则100Mo的衰变常数将相对于187Re的衰变常数发生变化。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。如果有足够的分析精度，我们将扩大研究范围，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.