Laser-based instrumentation for the detection of chemical agents

Evaluation of the detection of chemical agents and their simulants by synchronous detection of laser-induced flurescence (SDLIF) and laser-induced breakdown spectroscopy (LIBS) continued. The recently completed SDLIF apparatus was tested with a solution of tetracene in benzene. The conventional fluorescence spectrum of tetracene exhibits a bandwidth of approximately 90 nm, whereas the synchronously detected spectrum has a spectral width of only 7 nm. The potential impact of both spontaneous and stimulated Raman scattering on agent detection by SDLIF was investigated. Neither Raman process seemed to impose detection limitations. Extension of the spectral tuning range of the SDLIF system to wavelengths as short as 210 nm was begun. This capability is vital, because the absorption bands of most agents and their simulants are in this portion of the ultraviolet range. Further attempts to use LIBS to detect nascent CN radicals arising from molecules containing this species were unsuccessful.