2-D ABSOLUTE OH CONCENTRATION PROFILES IN ATMOSPHERIC FLAMES USING PLANAR LIF IN A BIDIRECTIONAL LASER-BEAM CONFIGURATION

A technique has been developed to measure the absolute OH concentratio n at atmospheric pressures by using a combination of direct absorption and laser-induced fluorescence (LIF) detection. The technique is inde pendent of collisions, because it uses laser beams in a bi-directional configuration, thereby eliminating collisional quenching. The absolut e OH concentration is measured spatially resolved in two dimensions by using absorption on the Q(1)(6) rotational line in the A(2) Sigma(+) (upsilon' = 0) <-- X-2 Pi(upsilon '' = 0) band of OH at 309 nm. The re quirements for obtaining a good signal-to-noise ratio for the techniqu e are discussed and the possibilities of single-shot measurements are investigated.