Broadband optical reflectance measurements of shock-compressed Si and Ti

Broadband optical reflectance spectra of shock-compressed materials have historically been difficult to obtain due to the mm spatial scales and ns timescales of experiments. Nonetheless, such spectra are useful for identifying phase transitions and understanding electrical conductivity of materials. A new diagnostic and experimental platform for the measurement of broadband reflectivity has been brought online at the OMEGA EP laser facility. The platform allows measurement of optical spectra in the 450-750 nm wavelength range. In this talk, recent results using this platform for shocked Si and Ti will be presented. The Si reflectance spectrum is found to change shape on shocking, indicating a change in the materials electronic structure at high pressure. The Ti reflectance spectrum is found to stay relatively constant as a function of pressure, supporting its use as a reflectivity standard in many previous experiments.