Nitro group asymmetric stretching mode lifetimes of molecules used in energetic materials

Picosecond infrared pump-probe measurements of the vibrational relaxation o f the nitro (NO2) functional group asymmetric stretch (similar to 1580 cm(- 1)) of several molecules used in energetic materials, TNAZ, RDX, HMX, and C L-20 (abbreviations defined in text), and nitromethane, are presented. In a ddition, a temperature-dependent study was performed between 50 and 298 EC on TNAZ. FLU of the lifetimes fall in the range of 2-6 ps with the exceptio n of nitromethane, which has a lifetime of 16 ps. The temperature dependenc e of TNAZ is flat and solvent independent, suggesting an intra-molecular re laxation pathway that does not involve low-frequency modes. (C) 1999 Elsevi er Science B.V. All rights reserved.