Study of tensile deformation in shocked Z-cut, α-quartz using time resolved Raman spectroscopy

An experimental method has been developed to use time resolved Raman spectroscopy as a microscopic probe of tensile deformation in shocked crystals. Tension is produced in the sample interior by the interaction of rarefaction waves generated in plate impact, uniaxial strain experiments. Optical fibers are used to transmit visible light from a pulsed laser to the sample and to transmit the scattered light to a recording system with 50 ns time resolution. The strain-induced shift of the 464 cm1, A1 line of α-quartz was measured. Results are presented for longitudinal stresses ranging from 54 kbar in tension to 60 kbar in compression. For each experiment, the 464 cm−1 line exhibited a shift toward higher frequency in compression, followed by a return to the ambient position upon unloading, followed by a comparable shift toward lower frequency in tension. This latter shift correlates to a marked increase in the intertetrahedral (Si–O–Si) bond angle of quartz with tension. Comparison with earlier work and the analysis presented here suggests that there is also significant distortion of the SiO4 tetrahedra and a mechanism for this distortion is proposed.