H₂ excitation diagrams normalized to the column density of H₂ obtained for shocks propagating at 5 (top panels) and 20 (bottom panels) km s⁻¹ in media with densities varying between 10³ (left panels) and 10⁵ (right panels) cm⁻³, a scaling factor of the UV radiation field of 1 (red), 10 (dark blue), 10² (light blue), 10³ (green), and 10⁴ (orange), and a buffer visual extinction . All non-varying parameters are set to their standard values (see Table 1). To estimate the effect of the UV pumping of the rovibrational levels of H₂, the models have been run with (filled circles) and without (dotted circles) this process. We note that only pure rotational levels exist below 5987 K. Above this limit, both pure rotational and rovibrational levels exist.