Photodissociation followed by laser-induced fluorescence at atmospheric pressure and 24 °C:: a unique scheme for remote detection of explosives

A unique scheme has been applied for sensitive remote detection of 2,4,6-trinitrotoluene (TNT) vapor trace amounts at atmospheric pressure and 24 degreesC. The detection concept is based on a single laser beam inducing a tandem process: photodissociation of TNT vapor followed by highly selective detection of its photofragments vibrationally excited NO, utilizing laser-induced fluorescence with the A(2)Sigma (+)(upsilon' = 0) <-- X(2)Pi(upsilon = 2) transition. A detection sensitivity of at least 8 parts in 10(9) of TNT vapor with a signal-to-noise ratio of approximately 10 has been experimentally verified for an unfocused similar to5-mJ laser beam, measured at a distance of similar to 15 cm from the TNT sample. (C) 2001 Optical Society of America.