Dependence of the mean derived CRIRs on the assumed values of ﹩{\chi }_{\mathrm{UV}}/{n}_{50}﹩ for ﹩Z={Z}_{\mathrm{std}}﹩ (solid curves) and ﹩Z=2\,{Z}_{\mathrm{std}}﹩ (dashed curves). Blue curves: mean CRIRs derived for diffuse molecular clouds (i.e., from ﹩{{\rm{H}}}_{3}^{+}﹩). Red curves: mean CRIRs derived for diffuse atomic clouds.