Low-pressure limiting and radiative association rate constants k₀, k_r as a function of the vibrational density of states of the adduct, ρ(E₀). The stars are the experimental k₀ values at 300 K, the open circles are the calculated k₀ values at 300 K from Vuitton et al. (2012), the diamond is the calculated k₀ value at 300 K performed for this study and the solid circles are the k_r calculations at 150 K from Vuitton et al. (2012). Units on the left axis are in cm⁶ molecule^-2 s^-1 for k₀ and cm³ molecule^-1 s^-1 for k_r. Experimental data are taken from: H + NH₂ (Gordon et al. 1971), H + CH₃ (Brouard et al. 1989), CH₃ + O₂ (Fernandes et al. 2006), CH₃ + NO (Kaiser 1993), CH₃ + NH₂ (Jodkowski et al. 1995), CH₃ + CH₃ (Slagle et al. 1988; Cody et al. 2002). The solid and dashed lines correspond to the general expression we derived for the low-pressure limiting rate constants k₀ for H addition and CH₃ addition, respectively. The dashed-dotted line corresponds to the general expression we derived for the radiative association rate constants k_r.