Laser-induced predissociative fluorescence: dynamics and polarization and the effect of lower-state rotational energy transfer on quantitative diagnostics.

摘要: Laser-induced predissociative fluorescence is often used for diagnostics because its short-lived upper states are minimally disturbed by collisions. We discuss the effects of lower-state collisions with parameters relevant to our atmospheric H2–O2 flame. A pulse tunable KrF excimer-laser light induces A←X,Q1(11), 3←0 transition in OH. measure intensity and polarization resulting ←X, Q1(11), 3 → 2 as a function laser brightness. simple model that uses no adjustable produces reasonable fit data. It predicts that, even at very modest energies, almost directly proportional rate constant rotational energy transfer (RET) within lower vibrational state. That can be strong local conditions. Furthermore, under typical operating conditions excimer will pump an amount OH out state many times large originally present. This occurs RET X-state continuously replenishes during pulse. Even when this occurs, signal may still vary linearly intensity, nearly expected weak pumping. At higher intensities, significant fraction measured arises from two-photon photodissociation water flame reaction.