Picosecond Studies of Condensed-Phase Energetic Materials
Final rept. 14 Mar 1982-14 Mar 1985
CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
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This report describes a series of picosecond spectroscopic investigations aimed at studying the reaction dynamics of condensed phase energetic materials. The emphasis of the experimental work focused on rotational reorientation of excited state molecules in solution. A number of results of relevance to the understanding of condensed phase energetic materials were obtained. Studies were made at elevated pressures up to 10kbar. The short time behavior of molecules under such conditions may be relevant to shock wave chemistry, and therefore, to energetic materials. The rotational behavior of molecules under these and other conditions were observed and compared with a variety of theoretical approaches. It was found that hydrodynamic models, which are fundamentally macroscopic in character, could be used to describe the short- time behavior of molecules. It was found that on this time scale, dielectric relaxation plays an important role in determining behavior of polar molecules. It was also observed that the molecular rotation times were independent of the excitation frequency. This was used to estimate the microscopic thermal conductivity of the solvent. Since the emission spectra are not observed to change with excitation energy, the excess vibrational energy in the molecule must be dissipated into the solvent in a few picoseconds. Once there, this heat might be expected to decrease the solvent viscosity.
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