9410695 Thonnard This award provides funding for the development of a laser-based resonance ionization spectroscopy technique capable of measuring the isotopic abundances of noble gas constituents krypton-81 and krypton-85 in natural samples. The project is to be carried out in the Institute for Rare Isotope Measurements at the University of Tennessee. Accurate measurements of the radionuclei of krypton-81 and krypton-85 can contribute to a better understanding of processes in the environment, including dating of polar ice and very old groundwater, deep ocean circulation rates, and modern water flow patterns. These isotopes have half-lives of 210,000 and 10.8 years respectively and are found in natural samples with isotopic abundances usually less than a part per trillion. Accurate analysis is a problem that has not yet been solved. The PI and colleagues on this project will develop a multi-step technique aimed at achieving an analytical procedure capable of measuring hundreds of environmentally significant samples per year. *** 9405805 Craig This award provides 75% of the funds required for the acquisition of a microscope system for use with transmitted and reflected light to be used in the rare gas isotope laboratory, Scripps Institution of Oceanography at the University of California, San Diego. The University is committed to providing the remaining funds necessary for the acquisition. The microscope system is mainly to be used by researchers working with fluid, glass, and crystalline inclusions trapped in samples of basaltic rocks that have been extruded from the Earth's mantle. The microscope is needed for the location and identification of these small inclusions prior to extraction of the rare gases (argon, helium, and neodymium) for isotopic analysis. The researchers at the Scripps Institution of Oceanography are using the isotopic content of the rare gases brought up from the mantle to understand the geochemical evolution of the mantle. ***
