An ambient air RF low-pressure pulsed discharge as an OH source for LIF calibration

A reference OH source for on-line, real-time calibration of OH laser-induced fluorescence (LIF) measurements, based on a pulsed N-2-H2O RF discharge, is described. Its operation principles are demonstrated together with its stability with respect to variations of discharge conditions and laser energy. Such stability is the basis for operation of the source under less controlled conditions. The correctness of the working principle is then demonstrated with a simple ambient air gas feed that greatly simplifies the source apparatus. This is an important requisite for operation in field instruments. The absolute OH density can be recovered with an error of about 20%.