Stimulated emission pumping of OH and NH in flames by using two-color resonant four-wave mixing

In this work we examine the analytical potential of two-color resonant four-wave mixing for the determination and characterization of trace elements in a combustion environment. Experimental results for NH and OH in flames at atmospheric pressure are presented. The selectivity of the technique is used to simplify the Q-branch region of the (0-0) A3Π−X3Σ− vibronic transition of NH. Furthermore, substantial signal-to-noise ratios in the (0-0) A2Σ+−X2Π system of OH are achieved. The high sensitivity is applied to perform stimulated emission pumping involving the weak (0–1) vibrational band. In addition, we demonstrate that the technique is sensitiive to state changing collisions.