OH laser-induced fluorescence at high pressures: Spectroscopic and two-dimensional measurements exciting the A-X (1,0) transition

Laser-induced fluorescence (LIF) spectra of OH were recorded in the exhaust of a laminar premixed methane/air flame in the pressure range betwen 5 and 36 bar. The OH A-X (1,0) transition near 280 nm was excited. From these spectra, temperatures and effective collisional broadening coefficients were determined by means of a detailed simulation programm. The strong dependence of the pressure broadening coefficient on the rotational quantum number had to be accounted for, in order to avoid systematic errors in the temperature determination. Strategies for temperature measurements at high pressures by two line measurements are presented. In order to demonstrate the applicability of the detection scheme discussed here for high-pressure applications, single-pulse two-dimensional measurements of the OH distribution at 36 bar are presented, as well as an averaged temperature distribution.