Model 1a χ structures and abundances relative to H-nuclei for atomic He, electron, H, H₂, H₂exc (v > 0), C⁺, C, CO, CH₄, OH, and H₂O. The contour plots in the ionized carbon abundance plot show log (χ/n), where χ is the enhancement with respect to the interstellar UV and n the total number of H-nuclei. In a few panels, dust temperature (T_d), gas temperature (water abundance panel), or extinction A_V contours are overplotted by dashed lines.