Accession Number : ADA305738

Title :   Laser-Induced Photofragmentation/Fragment Detection Spectrometry of Brominated Compounds.

Descriptive Note : Final rept. Jan 94-Dec 95,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Sausa, R. C. ; Simeonsson, J. B.

PDF Url : ADA305738

Report Date : MAR 1996

Pagination or Media Count : 38

Abstract : Studies have been performed to evaluate the analytical capabilities Of a novel, one-color, laser-induced photoframentation/fragment detection technique for the detection of ambient brominated compounds. Laser radiation at 260.634 nm is used to both fragment the brominated compounds and excite the characteristic Br atom photofragment via its two-photon 4p(4)5p(4)D(sup o) 3/2 left arrow 4p(5) (2)p(sup o) 3/2 transition. Detecton is accomplished by either (2+1) resonance-enhanced multiphoton ionization (REMPI), or by laser-induced fluorescence (LIF) or stimulated emission (SE) from the (4)p(4)5p (4)D(sup o)3/2 right arrow 4p(4)5s (4)p5/2,3/2 transition at 844 and 751 nm, respectively. The SE signal is coaxial to the laser beam and is approximately two orders of magnitude greater than the LIF signal at 844 nm. Measurements are performed in a photolysis cell at total pressures of 1-760 Torr. For REMPI detection, total (nonselective) ion collection is employed using a miniature pair of electrodes. The absorption cross section of the two-photon 4p(4)5p (4)D(sup o) 3/2 left arrow 4p(5) (2)p(sup o)3/2 transition is estimated to be 1.8 x 10(exp -45) cm (to the fourth power)seconds, and limits of detection in the ppb are obtained for CH3Br, CHBr3, and CHClBr2. Results are discussed and compared to those obtained by other techniques. jg p3

Descriptors :   *DETECTION, *LASER INDUCED FLUORESCENCE, *FRAGMENTS, *PHOTOFRAGMENT SPECTROSCOPY, *BROMINATION, EMISSION, IONS, RADIATION, STIMULATION(GENERAL), PHOTOLYSIS, MOLECULES, CELLS, EXCITATION, ATOMS, LASER BEAMS, ELECTRODES, RESONANCE, PHOTONS, ENERGY LEVELS, ABSORPTION CROSS SECTIONS, MINIATURIZATION, CHEMICAL COMPOUNDS, BROMINE, SPIN STATES.

Subject Categories : Inorganic Chemistry
      Organic Chemistry
      Radiation and Nuclear Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE