Continuous curves give the total CO cooling rate, as predicted by the approximate analytic formulation derived here (Eqs. (15) through (18)). The different panels correspond to (a) T = 10K ; (b) T = 20K; (c) T = 40K; and (d) T = 60K (these temperatures are given in the top lefthand corner of each panel). The different curves represent different values of (these values are given down the righthand margin of each panel). The rates obtained by the detailed computations of GL78 are given at discrete values of the density, ; plus signs, stars, open circles, crosses and open squares correspond respectively to .