Samples of diffuse [C ii]-w/o-CO and H i without [C ii] or CO for R_G<R_⊙. The gas pressures P₁, P₂, and P₃ in all panels a)–c) correspond to 3000, 6000, and 10⁴ K cm^-3, respectively. a) Scatter plot of [C ii] intensities verses H i intensities for each spaxel. The dashed lines represent the [C ii] intensities expected for H excitation of C⁺, corresponding to the H i intensity in each spaxel. The solid lines represent the 3σ detection limit for [C ii] in the 3 km s^-1 wide spaxels. b) Plot of the fraction of diffuse [C ii] spaxels ([C ii] without CO) in each H i intensity bin with [C ii] intensities in excess of that expected for excitation in the H i clouds (see text). c) Number distribution of H i spaxels without [C ii] or CO plotted against H i intensity for the sample of diffuse H i spaxels without [C ii] or CO. The dashed vertical lines indicate the minimum threshold H i intensity for detecting [C ii] for pressure models P₁, P₂, and P₃.