Raman spectra of shock compressed pentaerythritol tetranitrate single crystals: anisotropic response

To gain insight into the anisotropic sensitivity of shocked pentaerythritol tetranitrate (PETN) single crystals, single-pulse Raman spectroscopy was used to examine the response of crystals shocked along the 100] (insensitive) and 110] (sensitive) orientations. High-resolution Raman spectra revealed several orientation-dependent features under shock compression: (i) substantially different stress dependence of the Raman shift for the CH(2) and NO(2) stretching modes for the two orientations, (ii) discontinuity in the stress dependence of the Raman shift for the CH(2) stretching modes above 4 GPa for the 110] orientation, and (iii) large broadening for the CH(2) and NO(2) asymmetric stretching modes for stresses above 4 GPa for the 110] orientation. The present data in combination with previous static pressure results provide support for conformational changes in PETN molecules for shock compression along the 110] (sensitive) orientation. Implications of the present results for the anisotropic sensitivity of shocked PETN are discussed.