= Helium-3 relaxation time
{title2=$\tau^{-1}=2An_{3e}+B=\sqrt{B^2+4AC}$}
A small abundance displacement from the <helium-3 equilibrium abundance> obeys $\dot x=-x/\tau$ to linear order. Rapid relaxation relative to background evolution allows the abundance to track its equilibrium. If the equilibrium drifts, the displacement equation also contains $-\dot n_{3e}$. In the pp-I limit the rate is $n_1\sqrt{2\lambda_{11}\lambda_{33}}$, so both production and destruction <temperature> dependences matter.
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