TIME-RESOLVED RAMAN MEASUREMENTS IN ALPHA-QUARTZ SHOCKED TO 60 KBAR

An experimental method for obtaining time resolved Raman spectra in shock wave experiments is described. A key aspect of this method is the use of optical fibers to transmit light from a pulsed laser to the sample and to transmit the scattered light to the recording equipment. Using this method we have measured changes in the A1(466 cm-1) Raman line of alpha-quartz shocked along the z axis to 60 kbar. For the same density compression, the line shifts under shock loading are considerably larger than under hydrostatic loading. Because shifts of the A1(466 cm-1) line in quartz are correlated with changes in the Si-O-Si bond angle, which, in turn, is the primary compression mechanism in quartz, the present results indicate the role of nonhydrostatic stresses on compression at the molecular level.