US Government As Represented by the Secretary of the Army

Josef Simeonsson

Rosario C Sausa

George Lemire

An apparatus and method for the sensitive detection of atmospheric and/or surface absorbed nitrocompounds has been developed. The apparatus and method may be employed to detect the presence or absence of propellants, explosives, and nitropollutants. The unique feature herein is that the apparatus and method employ one laser operating at or near 226 nm. The laser photofragments the target molecule and facilitates the detection of the characteristic NO fragment, by resonance-enhanced multiphoton ionization (REMPI) and/or laser-induced-fluorescence (LIF) via its A.sup.2 .SIGMA..sup.+ -X.sup.2 II.sub.i transitions. The analytical utility of this apparatus and method has been demonstrated on numerous compounds, such as, DMNA, nitromethane, nitro-benzene, TNT, and RDX. With the present system, a limit of detection of 8 and 24 ppb is obtained for RDX and TNT, respectively, using only 100 micro-Joules per pulse of laser energy. Limits in the sub parts-per-trillion are projected using higher laser energies and improved system design.

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Elkridge, MD, United States of America

Josef Simeonsson