Time-resolved Raman spectroscopy of polystyrene under laser driven shock compression

The microscopic and dynamic response of the atactic polystyrene molecules under shock compression at laser power density of 4.9GW/cm(2) was studied using time-resolved Raman spectroscopy. The shock pressure estimated in the polystyrene sample was 2GPa, and the temporal and wavenumber resolutions in these experiments were 3ns and 3cm(-1), respectively. The shocked polystyrene showed a blue shift of 5 and 7cm(-1) for the 1004cm(-1) (C-C-C ring bending mode nu(12)) and 1606cm(-1) (C-C ring stretching mode nu(8a). , respectively. The changes in nu(12) and nu(8a) modes are observed with respect to shock wave propagation. It is observed that the intensities of the Raman peaks decrease and the FWHM of the modes increase due to formation of additional new peaks with delay. The reason behind this indicates the mechanical processes associated with the uniaxial nature of the shock compression. The shock velocity inside the polystyrene was calculated as 2.9 +/- 0.12km/s using the evolution of intensity ratio of peaks with time. This is in good agreement with the shock velocity (3.0km/s) deduced from the 2D simulations, performed using three temperature radiation hydrodynamic code, THRD. Copyright (c) 2017 John Wiley & Sons, Ltd.