CALIFORNIA INSTITUTE OF TECHNOLOGY|
Nuclear Chemistry research at CalTech is carried out in the Division of Geological and Planetary Sciences, concentrated on a wide variety of geochemical applications. This division actively solicits graduate student applications from persons with solid undergraduate training in Chemistry or Physics, and graduate requirements are tailored for such students. It is also possible for students admitted to the Division of Chemistry and Chemical Engineering to do thesis work in geochemistry with a member of the Geology/Planetary Sciences staff.
The traditional application of nuclear chemistry to geological problems was in the area of radioactive dating. Isotopic dating techniques are now well established, although their application to specific problems is not necessarily routine. CalTech continues to be a leader in geochronology, but much geochemical research at present involves more sophisticated use of isotopic data and nuclear techniques to geochemical problems.
Isotopic variations due either to radioactive decay or to physical, chemical, or biological stable isotope fractionation provide unique and quantitative clues to the history of the natural materials. The application of nuclear chemistry principles to the earth and planetary sciences remains a frontier area, with many exciting problems remaining to be solved.
In terrestrial, meteoritic, and lunar rocks, isotopic variations in Sr, Nd, Hf, and Pb are sensitive to the history of the materials from the formation of the parent planet until the time of formulation of the sample analyzed. In chondritic meteorites, isotopic variations may reveal the sites of nucleosynthetic processes in stars and supernovae that produced the input matter to the solar system. Isotopic studies on H, C, O, Si (S. Epstein); Mg, Ca, Ti, Cr, Sr, Ag, Ba, Nd, Sm, and U (G. J. Wasserburg) have revealed such variations, and have documented the existence of unmixed stellar inputs.
Th isotopic variations in sedimentary materials are being used to work out the chronology of the Ice Ages (G. J. Wasserburg). The O, H, and C isotopic properties of sedimentary materials contain a record of the Earth's climate in the past (S. Epstein). The O and H isotopic compositions of igneous rocks have been utilized to document important (both scientifically and economically) interactions between magmas and water (H. P. Taylor).
Analytical techniques based on nuclear chemistry dominate geochemistry at present. In this Division a wide variety of innovative applications are being carried out. For example, the microscale distribution of trace elements in rocks is being studied by fission and alpha track radiography and by the use of proton or synchrotron radiation induced X-rays. A primary application is to the study of the chemistry of actinide elements, especially Pu, in meteorites (D. S. Burnett). Stable isotope dilution mass spectrometry is being used to study the biogeochemical evolution of trace elements, especially Pb, through major biological food chains (C. C. Patterson). Depth sensitive charged particle nuclear reactions are being used as analytical tools for light element analysis and surface chemical studies (E. Stolper, D. S. Burnett).
For further information contact:
D. S. Burnett
Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA 91125