Research: Spectroscopy of
Minerals and other Phases
at High Pressure and or Temperature
The central theme of my research has been to use spectroscopy on solid state materials (much at high pressure) to gain a better understanding of their bulk thermoelastic properties as well as to examine changes in structure while under pressure. This work began in 1977 on MgO, and after a brief hiatus, continued in 1986 to the present. Materials studied include forsterite, enstatite, and all of their high pressure polymorphs. Several perovskites (both minerals as well as non-minerals; garnets, including 6 rock-forming garnets as well as YAG and binary solid solutions; the orthosilicates monticellite and fayalite; and the clinopyroxenes diopside and hedenburgite. New work includes amphiboles and feldspars. While work has centered on geophysically (geologically) relevant materials, the methods and analysis techniques are broadly applicable to a wide variety of materials.
The central purpose of the spectroscopy in my lab has been to obtain vibrational information useful for determining thermodynamic properties. This is a subset of possibilities. Laser spectroscopy can be performed on samples on the order of μ-meters. As a example, in situ detection of phases synthesized in a laser heated diamond anvil cell has proven very effective.
Experiemental work in the past has included both laser Raman and laser fluorescence spectroscopy. Many of the materials studied have been studied at high pressure while MgO has been studied at high temperature (1 atm so far) and high pressure and subambient temperatures (to 90 K).
The experimental capabilities here at UW are being expanded to include CO2-laser heating in the diamond anvil cell, both for synthesis of high pressure phases as well as measurement of the vibrational spectra at simultaneous high P and T.
Coming soon: a library of Raman and fluorescence spectra