Fast spectroscopy of energy release in nanometric explosives

A nanometric explosive containing 50–200 nm diameter Al particles and a nitrocellulose (NC) oxidizer is studied by high repetition rate picosecond laser ignition combined with time-resolved emission spectroscopy and coherent anti-Stokes Raman spectroscopy (CARS) of ONO2 stretching of the oxidizer. When the Al aggregates are flash-heated to the boiling point, 2740 K, nitro groups of the oxidizer near each hot aggregate are consumed within 500 ps. A burst of emission that indicates energy release occurs in ∼5 ns. The ignition delay is in the range of 500 ps to 3 ns. The rate-limiting step for energy release at Al-NC hot spots is vibrational relaxation of hot oxidized Al species.