Ratio of emission measures, ﹩{\mathrm{EM}}_{{\rm{H}}}/{\mathrm{EM}}_{{\rm{C}}}﹩, predicted by our diffuse clouds models as a function of the CRIR. Results are shown for five values of the UV radiation field, ﹩{\chi }_{\mathrm{UV}}/{n}_{250}=0.25﹩, 0.5, 1, 1,5, and 2.5, and for two values of the cloud extinction, ﹩{A}_{V}(\mathrm{tot})=1﹩ mag (dashed curves) and 5 mag (solid curves). Green curve: ﹩{\mathrm{EM}}_{{\rm{H}}}/{\mathrm{EM}}_{{\rm{C}}}﹩ predictions obtained using the simple SS87 analysis (see the text).