BROAD-BAND DEGENERATE 4-WAVE-MIXING OF OH FOR FLAME THERMOMETRY

Multiplex DFWM spectroscopy of OH using a broad-bandwidth modeless las er is reported. Temperatures are derived from single-shot and averaged multiplex spectra. The results are compared to those from DFWM spectr a obtained using a scanning narrow linewidth laser. System atic errors in derived temperatures arising from absorption are found to be small er for multiplex spectra than scanning narrowband spectra at equivalen t levels of saturation. The reduced sensitivity to absorption of broad band multiplex spectra is shown to be in agreement with results of a m odel of DFWM which includes non-degenerate contributions to the signal intensity.