= Effective recombination coefficient
{title2=$\alpha_\ell^{\rm eff}$}
The effective recombination coefficient for a <spectral line> counts recombinations and subsequent <radiative cascades> producing that line. At sufficiently low density, its photon production rate per volume is $n_en_{\rm parent}\alpha_\ell^{\rm eff}$. It depends on gas temperature, optical-depth assumptions such as <Case B recombination>, and sometimes density. It differs from the total rate coefficient removing the parent ion.
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