ROTATIONAL RELAXATION OF HIGH-N STATES OF OH (X(2)II, V=1-3) BY O-2

We have studied the relaxation of OH(X(2) Pi, v, N) produced by the re action O(D-1) + H-2 --> OH + H. Infrared emission measurements of the fundamental vibration-rotation band of OH were acquired at a temperat ure of 100 K in a large cryogenic chamber. Trace amounts of ozone were added to mixtures of H-2, O-2, and Ar at low (less than or equal to 3 8 mT) pressures. The ozone was photolyzed to produce O(D-1). Rapid rea ction with H-2 produced OH. Spectrally and temporally resolved emissi ons from levels up to the exothermic limit were observed with sufficie nt spectral resolution to permit kinetic analysis of individual level populations. The production rate was observed to scale as the rotation al quantum number except at the highest levels populated. At early tim es we observed inverted rotational state distributions that subsequent ly relaxed to form thermal distributions in each vibrational level. Un der these conditions, rotational relaxation was rapid in comparison wi th vibrational relaxation. Rotational relaxation within a given vibrat ional state could be represented by single quantum collisional exchang e at near-gas-kinetic rates. The rotational level dependence of the de duced relaxation was determined.