TESTING LINESHAPE MODELS - MEASUREMENTS FOR UPSILON=1-0 CO BROADENED BY HE AND AR

We present measurements of the spectral profiles of many P and R branc h lines in CO-He and CO-Ar mixtures, all at 301.5 K. The lineshapes ar e compared with several semi-classical models and in particular with m odels that include the speed dependence of both the translational moti on and the relaxation of the optical coherence. Using a correlated spe ed-dependent Galatry model proposed by Ciurylo and Szudy we find an ap parent reduction of the Dicke narrowing, amounting to almost 100% in s ome cases with a strong dependence on the rotational quantum number. H owever, while the parameters of this and several other models may be a djusted to fit the experimental data within the noise, no single model is free of criticism. Several shortcomings of existing models are dis cussed. Plots of broadening coefficients versus line number are also g iven. (C) 1997 Academic Press.