PRESSURE BROADENING AND COLLISIONAL NARROWING IN OH(V=1[-0) ROVIBRATIONAL TRANSITIONS WITH AR, HE, O-2, AND N-2

Line shapes are measured for OH(v = 1 <-- 0) transitions in the presen ce of Ar, He, O-2, and N-2 as a function of N rotational, spin-orbit, and lambda doublet states. Pressure broadening coefficients for all tr ansitions and buffer gases are determined from fits of the observed li ne shapes to the Voigt profile. The dependencies of the observed broad ening coefficients on the OH quantum levels are discussed and compared with previous pressure broadening studies in HF and NO. The observed OH line shapes are interpreted in terms of their impact on the determi nation of mesospheric and stratospheric OH populations, temperatures, and quantum state distributions from OH nightglow and dayglow emission . In the case of OH + Ar, evidence for Dicke narrowing is presented an d narrowing coefficients are reported from fits to a ''hard collision' ' model.