Laser photofragmentation/fragment detection studies on energetic materials

A sensitive technique. based on laser photofragmentation/fragment detection spectrometry is reported for the trace detection of energetic materials such as TNT, PETN, and. RDX. A single laser operating near 227 nm is used for both the photofragmentation of the parent molecule and detection of the characteristic NO fragment via its A-X (0,0) transitions near 227 nm, The fragment detection methods employed are resonance-enhanced multiphoton ionization with miniature electrodes and laser-induced fluorescence with a photodetector. Experiments are also conducted in the visible. region using 454-nm radiation for photofragmentation and fragment detection. The application of this technique in the trace analysis of the above-mentioned compounds at ambient pressure is demonstrated with limits of detection (S/N=3) in the range of sub- to low parts-per-million for a 20-sec integration time and 20-120 mu J of laser energy at 227 nm and similar to 5 mJ at 454 nm An increase in defection sensitivity is projected with an increase in laser energy and an improved system design.