Trace explosive residues are measured in real time by surface laser photofragmentation-fragment detection (SPF-FD) spectroscopy at ambient conditions. A 248-nm laser photofragments the target residue on a substrate, and a 226-nm laser ionizes the resulting NO fragment by resonance-enhanced multiphoton ionization by means of its A-X (0, 0) transitions near 226 nm. We tested two probes on selected explosives and modeled their electric field in the presence of a substrate with an ion optics simulation program. The limits of detection range from 1 to 15 ng/cm2 (signal-to-noise ratio of 3) at 1 atm and 298 K and depend on the electrode orientation and mechanism for NO formation.
© 2005 Optical Society of America
(140.3450) Lasers and laser optics : Laser-induced chemistry
(280.3420) Remote sensing and sensors : Laser sensors
(300.0300) Spectroscopy : Spectroscopy
(300.6360) Spectroscopy : Spectroscopy, laser
(300.6410) Spectroscopy : Spectroscopy, multiphoton
Jerry Cabalo and Rosario Sausa, "Trace detection of explosives with low vapor emissions by laser surface photofragmentation-fragment detection spectroscopy with an improved ionization probe," Appl. Opt. 44, 1084-1091 (2005)