QUANTUM BEAT SPECTROSCOPY OF OH RADICALS IN ATMOSPHERIC-PRESSURE FLAMES

Using time-resolved polarization spectroscopy we have observed quantum beats of coherently excited states in the (A(2) Sigma(+)-X(2) Pi) vib ronic (0, 0) band system of OH in atmospheric-pressure flames. With a spectral bandwidth of 1 cm(-1) of the tunable coherent light source em ployed, line splittings were deduced from the temporal beat structure. Depending on the rotational quantum number of the probed transition a nd the collisional environment the relaxation times of anisotropic ori entational distributions in which the quantum beat oscillations were o bserved ranged between 120 ps (J '' = 5) and 368 ps (J '' = 10).