Excitation rate coefficients ⟨σv⟩ for different models of inelastic collisions with neutral hydrogen atoms and with free electrons, and their ratios S, as functionsof the transition energy and at a fixed temperature. LCAO refers to Barklem (2016b); Impulse refers to Kaulakys (1991, Eq. (9)); Impulse-S refers to Kaulakys (1991, Eq. (18)); R-matrix refers to Barklem (2007); BSR refers to Tayal & Zatsarinny (2016; extended here to higher energies; see Sect. 2.4.3). The important 3s ⁵S^o → 3s ³S^o and 3s ⁵S^o → 3p ⁵P transitions have been highlighted.