In-situ spectroscopic observations of silicate vaporization due to >10 km/s impacts using laser driven projectiles

We present the results of shock‐induced silicate vaporization experiments using laser driven hypervelocity projectiles. In‐situ spectroscopic observations of shock‐heated quartz and diopside were conducted. We observed both atomic emission lines and blackbody continuum. Because emission lines occur only in a gas phase, this observation indicates that the incipient vaporization of silicates actually occurs at >10 km/s. We estimated the peak‐shock temperatures from the blackbody spectra. The obtained results suggest that the temperature dependence of the isochoric specific heat Cv depends rather strongly on material at extremely high pressures. Such difference in Cv dependence on temperature will influence the impact vaporization efficiency. Thus, investigation on the Cv of the other major silicates is necessary for understanding impact‐related phenomena. Furthermore, the observed high intensity of emission lines shows the possibility that a variety of the thermodynamic variables of expanding silicate vapor can be measured with a higher speed spectrometer.