Time resolved long-wave infrared laser-induced breakdown spectroscopy of inorganic energetic materials by a rapid mercury-cadmium-telluride linear array detection system.

A mercury-cadmium-telluride linear array detection system that is capable of rapidly capturing (∼1-5 s) a broad spectrum of atomic and molecular laser-induced breakdown spectroscopy (LIBS) emissions in the long-wave infrared region (LWIR, ∼5.6-10 μm) was recently developed. Similar to the conventional ultraviolet-visible LIBS, a broadband emission spectrum of condensed phase samples covering a 5.6-10 μm spectral region could be acquired from just a single laser-induced micro-plasma. Intense and distinct atomic and molecular LWIR emission signatures of various solid inorganic energetic materials were readily observed and identified. Time resolved emissions of inorganic energetic materials were studied to assess the lifetimes of LWIR atomic and molecular emissions. The LWIR atomic emissions generally decayed fast on the scale of tens of microseconds, while the molecular signature emissions from target molecules excited by the laser-induced plasma appeared to be very long lived (∼millisecond). The time dependence of emission intensities and peak wavelengths of these signature emissions gave an insight into the origin and the environment of the emitting target species. Moreover, observed lifetimes of these LWIR emissions can be utilized for further optimization of the signal quality and detection limits of this technique.