ULTRAFAST RAMAN-SPECTROSCOPY OF SHOCK FRONTS IN MOLECULAR-SOLIDS

The passage of a 4 GPa shock front through an embedded optical nanogau ge, a thin (similar to 700 nm) layer of polycrystalline molecular mate rial (anthracene), is monitored in real time by picosecond coherent Ra man scattering. Analysis of high resolution Raman spectra shows the sh ock rise time is less than 25 ps, and the front is less than 100 molec ules wide. The rise time is faster than relaxation of nonequilibrium p opulations of molecular vibrations, which shows a shock front in a mol ecular material can leave highly nonequilibrium vibrational states in its wake. The implications for shock initiation of energetic materials , typically polycrystalline molecular solids, are briefly discussed.