OH absorption spectroscopy in a flame using spatial heterodyne spectroscopy.

We demonstrate measurements of OH absorption spectra in the post-flame zone of a McKenna burner using spatial heterodyne spectroscopy (SHS). SHS permits high-resolution, high-throughput measurements. In this case the spectra span approximately 308-310 nm with a resolution of 0.03 nm, even though an extended source (extent of approximately 2x10(-7) m(2) rad(2)) was used. The high spectral resolution is important for interpreting spectra when multiple absorbers are present for inferring accurate gas temperatures from measured spectra and for monitoring weak absorbers. The present measurement paves the way for absorption spectroscopy by SHS in practical combustion devices, such as reciprocating and gas-turbine engines.