Picosecond dynamics of shock compressed and flash-heated nanometer thick films of δ-HMX

[摘要] Progress towards probing molecular dynamics of octahydro-1,3,5,7-tetranitro-1,3,4,7-tetrazocine (HMX) subjected to shock compression of a few GPa and/or temperature excursions exceeding thermal decomposition values (T > 500 K) is described. Due to shock velocities of a few nm/ps, nanometer-thick layers are needed for picosecond time resolution. Therefore, 5-10 nm thick films of S-HMX were deposited on metallic substrates with a template of a 4-nitrobenzoic acid monolayer. A polymer layer a few microns thick was spin-coated on top of S-HMX for shock confinement. The monolayer and HMX layer were probed simultaneously utilizing an ultrafast nonlinear coherent vibrational spectroscopy, termed vibrational sum-frequency generation (SFG). Shock pressures were estimated via comparisons with the monolayer nitro transition frequency blueshift in hydrostatic pressure measurements. Temperature determinations were made based on the reflectance of the metallic substrate.

[发布机构] School of Chemical Sciences, Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana; IL; 61801, United States^1

[关键词] 4-Nitrobenzoic acids;Coherent vibrational spectroscopy;Nanometer-thick films;Temperature determination;Temperature excursions;Transition frequencies;Ultrafast nonlinear;Vibrational sum-frequency generations