Collisional ionization equilibrium
= Collisional ionization equilibrium
{title2=$n_iC_i(T)=n_{i+1}\alpha_{i+1}(T)$}
In <collisional ionization equilibrium>, collision-driven <ionization> and recombination balance for the populated ion stages, determining their relative abundances at a given temperature. The resulting cooling curve includes the loss of line-emitting bound states as temperature increases. Rapidly cooling gas or external photoionization can invalidate this equilibrium assumption.