Molecular response of liquid nitrogen multiply shocked to 40 GPa

Liquid nitrogen was subjected to multiple shock compression to examine its response to pressures (15-40 GPa) and temperatures (1800-4000 K) previously unexplored in static and shock compression studies. Raman spectroscopy measurements were used to characterize the molecular bond response and to determine temperatures in the peak state. By extending our analysis to include other Raman spectroscopy measurements, an empirical relation was developed that describes the pressure and temperature dependence of the Raman shift (of the 2330 cm(-1) mode) for both shock and static compression. Based on the P-T dependence of the Raman shifts, the liquid nitrogen molecular response is best understood by considering three temperature regimes: below 1500 K, 1500-4000 K, and above 4000 K. For the pressures and temperatures accessed in the present work, liquid nitrogen remains a molecular fluid, and becomes a grey-body emitter at the highest pressures. (C) 2014 AIP Publishing LLC.