Notes: Critical densities (n_crit) for the Cloudy excitation model are calculated using Einstein A-coefficients and collisional strengths from Verner et al. (1999), evaluated at T = 7000 K for consistency with previous shock studies (e.g., Koo et al. 2016). The critical density is defined as n_crίt = Σ A_ki/ Σ C_ki, where A_ki is the spontaneous emission rate and $C_{ki}=\beta {\Omega }_{ki}\left(T\right)/\left(g_k\sqrt{T}\right)$ is the collisional de-excitation rate. Here, Ω_ki(T) is the collision strength, ɡ_k the statistical weight of the upper level, and β = 8.63 × 10⁻⁶ a constant. The sums run over all radiative (k > i) and collisional (k ≠ i) transitions from level k.