Accession Number : ADA289947

Title :   Spectrometric Studies of Selected Nitrocompounds Using Laser-Induced Photofragmentation/Photoionization at 193 nm.

Descriptive Note : Final rept. Aug 93-Feb 94,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Sausa, Rosario C. ; Simeonsson, Josef B. ; Lemire, George W.

PDF Url : ADA289947

Report Date : NOV 1994

Pagination or Media Count : 35

Abstract : A new method for detection trace vapors of NO2 containing compounds near atmospheric conditions has been demonstrated using one color laser photofragmentation/fragment ionization spectrometry. An ArF laser is employed to both photolytically fragment the target molecules in a collision-free environment and ionize the characteristic NO fragments. The production of NO is hypothesized to result from a combination of two NO2 unimolecular fragmentation pathways, one yielding NO in its X(2)Pi electronic ground state and the other in its A(2)Sigma+ excited state. Ionization of ground state NO molecules is accomplished by resonance-enhanced multiphoton ionization processes via their A(2)Sigma <-X(2)Pi (3,0), B(2)Pi <-X(2)Pi (7,0), and/or D(2)Sigma+ <- X(2)Pi (0,1) bands at 193 nm. The analytical utility of this method is demonstrated in a molecular beam time-of-flight apparatus. Limits of detection range from the parts-per-million (ppm) to parts-per-billion (ppb) level for NO, NO2, CH3NO2, dimethylnitramine (DMNA), ortho- and meta-nitrotoluene, nitrobenzene, and trinitrotoluene (TNT). Under effusive beam experimental conditions, discrimination between structural isomers, ortho-nitrotoluene and meta-nitrotoluene, has been demonstrated with the use of their characteristic photofragmentation/photoionization mass spectra. (jg)

Descriptors :   *SPECTROMETRY, *LASER APPLICATIONS, *PHOTOIONIZATION, *NITRO RADICALS, DETECTION, PRODUCTION, WEATHER, FRAGMENTATION, PHOTOCHEMICAL REACTIONS, METHYL RADICALS, PHOTOLYSIS, MOLECULES, STRUCTURAL PROPERTIES, VAPORS, EXCITATION, TARGETS, LASERS, MOLECULAR BEAMS, ISOMERS, IONIZATION, GROUND STATE, NITROGEN OXIDES, ARGON LASERS, FLUORIDES, EFFUSION, TNT, ATMOSPHERES, COLLISIONS, NITROBENZENES, PHOTOFRAGMENT SPECTROSCOPY, NITRAMINES, MASS SPECTRA, TRACE GASES, NITROTOLUENES.

Subject Categories : Inorganic Chemistry
      Organic Chemistry
      Physical Chemistry
      Radiation and Nuclear Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE