Acquisition of a Laser Raman Spectrometer for Studies on Phase Transition and Melting Silicate Minerals and Glasses at Ultra-high Temperature.

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This award provides funds for one-half the cost of acquiring a time-resolved laser Raman spectrometer system that will be installed and operated in the Department of Geological Sciences at the University of Washington. The University of Washington is committed to providing the remaining half required. The instrument system will be used to study the microscopic mechanism and dynamics of solid-state phase transitions and of melting in silicates at temperatures up to 3000K. Localized heating of the sample will involve radiation by a continuous- power CO2 laser, with the silicate crystals or glass acting as its own crucible container. Intense black-body radiation from the sample at high-temperature will be suppressed using a synchronous detection technique that involves pulsed-excitation and gated-array detection. The sample temperature will be determined from Raman intensities by Stokes/antiStokes ratioing and by means of a two color optical pyrometer. The high- temperature Raman spectra will be interpreted by molecular dynamics simulations. The molecular level structures of silicates at high-temperature are vital data for interpreting the nature of melting and other phase transitions inside the Earth.