Measurement of radical-species concentrations and polycyclic aromatic hydrocarbons in flames by fluorescence and absorption using a tunable dye laser. Progress report, March 1, 1980-February 28, 1981

Technical Report · Sun Mar 01 04:00:00 EST 1981

DOI:https://doi.org/10.2172/6535144· OSTI ID:6535144

Lucht, R P; Sweeney, D W; Laurendeau, N M

A theoretical and experimental investigation of OH saturated fluorescence is described. The goal of the research is to develop a saturated fluorescence technique which will yield accurate molecular number densities over a wide range of flame pressure, temperature, and composition. Experimentally, OH is excited by a ten nanosecond pulse from a Nd:YAG-pumped dye laser tuned to an isolated rotational transition in the (0,0) band of the A/sup 2/..sigma../sup +/-X/sup 2/ pi electronic system. The resulting fluorescence signal is resolved both spectrally and temporally. Total OH number densities are calculated by collecting fluorescence from the directly excited upper rotational level, and using the balanced cross-rate model to analyze the experimental data. Fluorescence measurements of OH number density agree to within a factor of three with the results of independent OH absorption measurements. Significantly, the ratio of the fluorescence signal to the number density measured by absorption is nearly the same in 30, 100 and 250 torr H/sub 2//O/sub 2//N/sub 2/ flat flames, demonstrating the insensitivity of the saturated fluorescence signal to the quenching environment of the radical. Collisional transfer in excited OH is studied by recording the time development of OH fluorescence spectrum. The experimental spectra are compared with the results of time-dependent computer modeling. By varying rotational transfer rates until the calculated and experimental spectra agree, rotational transfer cross sections can be calculated. The signal processing system was thoroughly checked by comparing the photomultiplier output to that of a fast photodiode, and by comparing single pulse Rayleigh scattering and fluorescence traces with sampling oscilloscope traces.

• Research Organization: Purdue Univ., Lafayette, IN (USA). School of Mechanical Engineering
• DOE Contract Number: AS02-78ER04939
• OSTI ID: 6535144
• Report Number(s): DOE/ER/04939-T1; COO-4939-3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400104 -- Spectral Procedures-- (-1987)
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
CHEMICAL REACTIONS
COMBUSTION
COMPARATIVE EVALUATIONS
DYE LASERS
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION SPECTROSCOPY
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FLAMES
FLUORESCENCE
FLUORESCENCE SPECTROSCOPY
HYDROGEN
HYDROXYL RADICALS
LASER RADIATION
LASERS
LUMINESCENCE
MATHEMATICAL MODELS
NEODYMIUM LASERS
NITROGEN
NONMETALS
OXIDATION
OXYGEN
RADIATIONS
RADICALS
RESEARCH PROGRAMS
ROTATIONAL STATES
SOLID STATE LASERS
SPECTROSCOPY
THERMOCHEMICAL PROCESSES