Local abundances of H₂, electrons, ﹩{{\rm{H}}}_{2}^{+}﹩ and H₃⁺ relative to H nuclei, and of H₂⁺ and ﹩{{\rm{H}}}_{3}^{+}﹩ relative to H₂, as a function of depth into a cloud of total visual extinction ﹩{A}_{{\rm{V}}}(\mathrm{tot})=8﹩ (i.e., ﹩{A}_{{\rm{V}}}(\mathrm{tot})=4﹩ to the midplane) exposed to UV radiation with ﹩{\chi }_{\mathrm{UV}}/{n}_{250}=1﹩. Results are shown for several values of the CRIR (see legend in top left panel). In the bottom right panel, which shows ﹩n({{\rm{H}}}_{3}^{+})/n({{\rm{H}}}_{2})﹩, the dashed lines indicate predictions of the analytic treatment adopted by IM12 (see our Equation (4)), for an assumed gas temperature of 70 K.