= Electron-hydrogen normalization of the cooling function
{title2=$\mathcal C=n_en_H\Lambda_{eH}$}
In an <optically thin> <plasma>, one convention defines the <radiative cooling> power per volume by $\mathcal C=n_en_H\Lambda_{eH}(T)$, where $n_H$ counts <hydrogen> nuclei. A convention $\mathcal C=n_H^2\Lambda_{HH}$ instead has $\Lambda_{HH}=(n_e/n_H)\Lambda_{eH}$. Thus the tabulated functions differ even for the same <gas>. With total particle <density> $n$, a monatomic-gas <radiative gas cooling time> is $3nk_BT/(2\mathcal C)$ when heating is negligible.<Thermal radiation processes by Jelle S. Kaastra and others>[§8: emission-measure normalization and cooling time]{ref}
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