Laser-induced Fluorescence of Photodissociation Products of Liquid-drop Triethyl Phosphate on a Surface

The paper studies a possibility of remote detection of surface traces of organophosphates using the double-pulse laser fragmentation/laser-induced fluorescence (LP/LIF) method. For liquid-drop traces of triethyl phosphate on a paper surface, the inertial character of origination of characteristic PO fragments (phosphorus oxide molecules) of organophosphates is shown. The concentration of formed fragments is maximal in approximately 2 μs after the action of a fragmenting laser pulse (266 nm). It is found that a delay of 2 μs between a laser pulse (247.78 nm) and a fragmenting pulse multiply increases the fluorescence intensity, by approximately 7 times compared to the single-pulse excitation method and approximately 2.3 times compared to simultaneous double-pulse action. Our experimental data confirm, first, a possibility of remote detection of surface traces of liquid-drop organophosphates by the two-pulse LF/LIF method and, second, a need in organizing optimal laser exposure conditions to increase the efficiency of the LF/LIF process. The results contribute to the knowledge about the efficiency of detecting organophosphate traces on other carrier surface types.