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

Colorado State University, Fort Collins CO

Investigators

Abstract

Hannah EAR-0307352 The 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.