Real-time, Laser-based Sensors for Military and Civilian Applications

We report on a novel laser-based technique coined surface laser photofragmentation-fragment detection (SPF-FD) spectroscopy for detecting explosives residues, chemical warfare agents, and other hazardous materials on surfaces in real time at ambient conditions. Our technique utilizes one or two lasers to both photolyze the target species and to facilitate the detection of the characteristic photofragments by resonance-enhanced multiphoton ionization, laser induced fluorescence, or both. We demonstrate its analytical utility on explosives RDX, HMX, CL20, and TNT, and report the effects of laser photofragmentation wavelength and energy, delay between photofragmentation and probe lasers, and electrode orientation on signal intensity. Signal to noise analyses yield limits of detection in the range of 1 to 15 ng/cm (S/N=3) at 1 atm and 298K.