Accession Number : ADA334669

Title :   Degenerate Four-Wave Mixing Spectroscopy in Collisionally Dominated Environments: Theory and Application

Descriptive Note : Final rept.

Corporate Author : AIR FORCE RESEARCH LAB BOLLING AFB DC

Personal Author(s) : Williams, Skip

PDF Url : ADA334669

Report Date : JAN 1994

Pagination or Media Count : 156

Abstract : The potential of degenerate-four wave mixing (DFWM) spectroscopy for the analysis of molecular species in high-pressure, high-temperature environments has been explored theoretically and experimentally. In addition, the reliability of DFWM has been assessed by comparing to laser induced fluorescence (LIF) measurements under the same experimental conditions. The results of these studies suggest that DFWM can provide quantitative information regarding trace molecular species in environments in which collisions and source emission hinder analysis by other means. DFWM has been used to detect the CH radical in an atmospheric-pressure oxyacetylene flame via the (0,0) and (1,1) bands of the A2 delta-X2 Pi system. The CH radical is a minor flame species and is important for understanding the primary reaction zone of many combustion environments. We have observed CH radicals with comparable sensitivity by both DFWM and LIF. From these measurements, we estimate a DFWM detection limit of 4 x 10(exp 11) molecules/ cu cm (4 x 10(exp 9) molecules/cu cm per quantum-state) for CH at atmospheric pressure. Vibrational temperatures and concentration profiles of CH obtained by both techniques are in good agreement.

Descriptors :   *SPECTROSCOPY, *METHYL RADICALS, *MOLECULAR PROPERTIES, *COLLISIONS, EMISSION, VIBRATION, DETECTION, LASER INDUCED FLUORESCENCE, MOLECULES, HIGH TEMPERATURE, THESES, HIGH PRESSURE, SENSITIVITY, COMBUSTION, RELIABILITY, QUANTUM ELECTRONICS, FLAMES, BAROMETRIC PRESSURE.

Subject Categories : Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE