Departure coefficients across the ⟨3D⟩ model atmosphere, for the lowest 42 terms of C 1 (up to 2s² 2p 4d ³P^o) as well as the ground state of C II. A solar carbon abundance of log ɛ_C = 8.43 was assumed. The low-excitation levels indicated in the plot span the ground state up to 2s.2p ^{3 5} S^o (4.18 eV), while the high-excitation levels indicated in the plot span 2s².2p.3p ¹P (8.54 eV) up to the ionisation limit (11.26 eV). The intermediate-excitation levels are those levels between them: 2s².2p.3s ³P^o (7.49 eV), 2s².2p.3s ¹P^o (7.68 eV), and 2s.2p^{3 3}D^o (7.95 eV). Departure coefficients are shown for the standard model atom (Fig. 3). The impact of collapsing fine structure, and of removing neutral hydrogen impact excitation, are also shown.