Shock wave experiment gives us deep insights in predicting the behavior of materials under extreme pressure and temperature conditions. These studies are of fundamental importance for geophysics, astrophysics, Inertial confinement and also have many technological applications[1]. Laser driven shock experiments have the additional advantages of repeatability, stability, low sample requirements and ease of synchronization. Insitu vibrational spectroscopy provides essential information on shock induced phenomena such as chemical reactions, intermolecular interactions and structural phase transitions.[2] Raman spectroscopy in particular enables us to examine molecular changes associated with shock induced structural and chemical transformation.

Benzene is prototype of aromatic compounds, and its phase and chemical transformation under pressure is one of the most extensively studied examples [3]. In this work we have performed High pressure Raman spectroscopy of Laser driven shock compressed Benzene upto 1.6 GPa using a pump-probe technique to examine shock induced structural or chemical changes under single shock conditions. The shock wave is generated by direct irradiation of a Q-switched Nd:YAG nanosecond pulsed laser of energy 2J and 8 ns pulse width using a glass confined target geometry. In the shock experiments performed here we studied the ring breathing mode of Benzene under shock compression. At a pressure of 1 GPa the observed mode showed a pressure induced blue shift of 14 cm^-1.

References:

[1] Physics and applications of laser-shock processing, J.Laser Appl., 10, p 265-279, (1998)

[2] Ultrahigh time-resolution vibrational spectroscopy of shocked molecular solids, J appl Phys, 81,p 2157-2166,(1997)

[3] Carbon Disulphide assisted polymerization of Benzene, J. Phys. Chem.B, 116, p 2414-2419, (1994)