Vibrational Energy Transfer in High Explosives: Nitromethane

Abstract

Time resolved vibrational spectroscopy with picosecond tunable mid-infrared pulses is used to measure the rates and investigate the detailed mechanisms of multiphonon up-pumping and vibrational cooling in a condensed high explosive, nitromethane. Both processes occur on the ˜100 ps time scale under ambient conditions. The mechanisms involve sequential climbing or descending the ladder of molecular vibrations. Efficient intermolecular vibrational energy transfer from various molecules to the symmetric stretching excitation of NO2 is observed. The implications of these measurements for understanding shock initiation to detonation and the sensitivities of energetic materials to shock initiation are discussed briefly.

Decomposition of some polynitro arenes initiated by heat and shock

“…However, in the case of shock wave-exposed TNT or its detonation, their formation cannot be interpreted as resulting from the action of heat. Many recent papers have dealt with this and related problems in energetic materials (for example, [22][23][24][25][26][27][28][29][30]). An idea about the initiation of detonation reads as follows: the excitation of crystal lattice vibration (phonons) after receiving impact or shock [23,27,28] is converted into bond stretching frequencies (vibrons) with subsequent spontaneous localization of vibrational energy in the nitro (explosophore) groupings [23,24].…”

First-principles band gap criterion for impact sensitivity of energetic crystals: a review

“…According to Klimenko and Dremin [68][69][70][71], the kinetic energy of the shock in this compression is accumulated through translational-vibrational relaxation processes. This or similar ideas have been applied by a number of authors in their studies of shock reactivity of energetic materials [72][73][74][75][76][77]. Dremin compares this initiation with initiation of photochemical reaction [78].…”

New aspects of initiation reactivities of energetic materials demonstrated on nitramines

“…thermal decomposition) in classical sense has no application in the process of detonation initiation by shock or impact. Many recent papers dealt with this and related problems (for example, [5][6][7][28][29][30][31][32][33][34]57]). An idea about the initiation of detonation which could be nearest to these facts is as follows: excitation of crystal lattice vibration (phonons) after receiving impact or shock [28][29][30] then be converted into bond stretching frequencies (vibrons) with subsequent spontaneous localization of vibrational energy in the nitro (explosophore) groupings [31,32].…”

“…Many recent papers dealt with this and related problems (for example, [5][6][7][28][29][30][31][32][33][34]57]). An idea about the initiation of detonation which could be nearest to these facts is as follows: excitation of crystal lattice vibration (phonons) after receiving impact or shock [28][29][30] then be converted into bond stretching frequencies (vibrons) with subsequent spontaneous localization of vibrational energy in the nitro (explosophore) groupings [31,32]. Similar, but more detailed description of this initiation is presented by another idea about electronic excitations facilitated by edge dislocations in explosive solids which was obtained from application of physics of the solid-state aspect to the study of pre-explosion state of heavy metal azides [33,34].…”

“…Outputs from the above-mentioned studies are subsequently compared with some findings of molecular dynamic approach to problems of initiation [28][29][30][31][32] as well as with some results of physics of solid-state application to this problem [33,34].…”