Time-Resolved Vibrational Spectroscopy of Polytetrafluoroethylene Under Laser-Shock Compression

Abstract

Shock-wave-induced high pressure and nanosecond time-resolved Raman spectroscopic experiments were performed to examine the dynamic response of polytetrafluoroethylene (PTFE) in confinement geometry targets. Time-resolved Raman spectroscopy was used to observe the pressure-induced molecular and chemical changes on nanosecond time scale. Raman spectra were measured as a function of shock pressure in the 1.2–2.4 GPa range. Furthermore, the symmetric stretching mode at 729 cm–1 of CF2 was compared to corresponding static high-pressure measurements carried out in a diamond anvil cell, to see if any general trend can be established. The symmetric stretching mode of CF2 at 729 cm–1 is the most intense Raman transition in PTFE and is very sensitive to change in pressure. Therefore, it can also be utilized as a pressure gauge for large amplitude shock wave compression experiments. A maximum blueshift of 12 cm–1 for the 729 cm–1 vibrational mode has been observed for the present experimental pressure range. A comparative study on the similarities and differences from the earlier work has been done in detail. One-dimensional radiation hydrodynamic simulations were performed to validate our shock compression results and are in very good agreement.