Top panel: equilibrium temperature and densities of H, H⁺, H₂, ${\text{H}}_2^{+}$+, e⁻, He, He⁺, He(2^>3S), and HeH⁺ obtained for an isobaric (gas pressure ~2.16 × 10⁹ K cm⁻³) CLOUDY model with an initial total hydrogen nuclei density n(H_tot) = 2.61 × 10⁴ cm⁻³ as function of the distance from the star starting from the illuminated face into the depth of the cloud. Bottom panel: zoomed-in view of the top panel in the region close to the Strömgren radii (within the black-colored dashed rectangle).