Time-resolved products observed from high pressure deflagrating energetic materials using femtosecond IR spectroscopy

What transient chemical species occur on the nanosecond to microsecond time-scale after an energetic material begins to deflagrate under Chapman-Jouguet conditions? What are the molecular lifetimes of transient species under similar conditions? Using ultrafast infrared spectroscopy to study the transient chemical phenomena of materials encapsulated in high-pressure diamond anvils cells (DACs), these and related questions can be addressed. Here we present a broadband time-resolved IR (TRIR) absorption technique applied to high-pressure deflagrating energetic materials. A 10 nanosecond laser pulse is introduced onto the surface of a high-pressure energetic material. After an induction period of approximately one microsecond the energetic material begins to deflagrate (1500+K) at subsonic velocities radially away from the laser ignited region. A mid-IR femtosecond laser pulse (pulse-gated, 2-10 micron tunable range) is transmitted through the deflagration front. The single-shot mid-IR absorbance is used to detect transient species. Our measurements provide a rigorous test of computational chemistry models.