Accession Number : ADA328140

Title :   (2+2) Resonance-Enhanced Multiphoton Ionization (REMPI) and Photoacoustic (PA) Spectroscopic Detection of Nitric Oxide (NO) and Nitrogen Dioxide (NO2) Near 454nm.

Descriptive Note : Final rept. Jan 96-Jan 97,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Sausa, R. C. ; Pastel, R. L.

PDF Url : ADA328140

Report Date : JUL 1997

Pagination or Media Count : 40

Abstract : Trace concentrations of NO and NO2 are detected with a dye laser operating near 454 nm. NO is detected by a (2 + 2) resonance-enhanced multiphoton ionization process by means of NO A (2)sigma(+)-X (2)Pi(0, 0) transitions with miniature electrodes, and NO2 is detected by a one-photon absorption photo acoustic process by means of NO2 A(tilde)' (2)B1(0, 8, 0) - X(tilde) (2)A1(0, 0, 0) transitions with a miniature microphone. Rotationally resolved excitation spectra show that the spectral resolution is sufficiently high to identify these species at 1 atm. The technique's analytical merits are evaluated as functions of concentration, pressure, and laser intensities. Low laser intensities favor NO2 photoacoustic detection whereas high laser intensities favor NO ionization. Limits of detection (signal-to-noise ratio 3) of 160 parts in 10(exp 9) for NO and 400 parts in 10(exp 9) for NO2 are determined at 1 atm for a 10-s integration time. Signal response and noise analyses show that three decades of NO/NO2 mixtures can be measured with a computational relative error in concentration that is three times the relative error in measuring the NO and NO2 signals.

Descriptors :   *DETECTION, *SPECTROSCOPY, *RESONANCE, *IONIZATION, *PHOTONS, *NITROGEN OXIDES, *NITROGEN DIOXIDE, COMPUTATIONS, AIR POLLUTION, EXCITATION, RESOLUTION, LASERS, SIGNALS, ELECTRODES, ERRORS, POLLUTANTS, DYE LASERS, ABSORPTION, MICROPHONES, HAZARDOUS MATERIALS, LOW INTENSITY, MINIATURE ELECTRICAL EQUIPMENT, NOISE ANALYZERS.

Subject Categories : Inorganic Chemistry
      Acoustics
      Atomic and Molecular Physics and Spectroscopy
      Air Pollution and Control

Distribution Statement : APPROVED FOR PUBLIC RELEASE