Ultrafast Dynamics of Shock Waves in Polymers and Proteins: The Energy Landscape

A 4.5 GPa shock pulse producing a cycle of compression heating $(<25\mathrm{ps})$ and expansion cooling $\left(\mathrm{\sim }1.5\mathrm{ns}\right)$ is used to study fast mechanical dynamics of solid organic polymers and proteins. Coherent Raman spectroscopy of a dye in the sample shows that compression occurs by an instantaneous part followed by a second, $\mathrm{\sim }300\mathrm{ps}$, structural relaxation process. After expansion, a mechanically distorted structure is produced which does not relax on the $<15\mathrm{ns}$ time scale. The results are interpreted with an energy landscape model.