Accession Number : ADA328143

Title :   Detection of Ambient NO by Laser-Induced Photoacoustic Spectroscopy Using A(2)Sigma(+)- X(2)Pi (0,0) Transitions Near 226 nm,

Descriptive Note : Final rept. Sep 95-Sep 96,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

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

PDF Url : ADA328143

Report Date : AUG 1997

Pagination or Media Count : 38

Abstract : Trace concentrations of NO are detected under ambient conditions by laser-induced photoacoustic spectroscopy. NO is excited via its A(2)sigma(+)-X(2)Pi (0,0) band with radiation near 226 nm, and the subsequent heat released is monitored by a microphone. Rotationally resolved photoacoustic spectra are recorded and fit using a multiparameter computer simulation based on a Boltzmann distribution. Transition probabilities and rotational energies are used as input parameters. The effect of buffer gas pressure, buffer gas, laser energy, and NO concentration on PA signal is investigated both experimentally and by model calculations. Units of detection of 1.2,2.8, and 4.9 ppm are obtained for NO in Ar, N2, and air, respectively. The ultimate sensitivity of this approach is greater with LODs projected in the low parts per billion by utilizing higher laser energies and an improved system design. The results are compared with previous studies using complementary laser-based spectroscopic techniques.

Descriptors :   *SPECTROSCOPY, *LASER APPLICATIONS, *TRANSITIONS, *NITROGEN COMPOUNDS, COMPUTERIZED SIMULATION, BUFFERS, INPUT, COMPUTATIONS, DETECTION, MODELS, PARAMETERS, PROBABILITY, ENERGY, RESOLUTION, GASES, PRESSURE, ENERGETIC PROPERTIES, ROTATION, OZONE, MICROPHONES, BOLTZMANN EQUATION, ATMOSPHERIC CHEMISTRY, ACID DEPOSITION, SMOG.

Subject Categories : Atmospheric Physics
      Inorganic Chemistry
      Lasers and Masers
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE