Bateman equation
= Bateman equation
{c}
{title2=$N_i'=-\lambda_iN_i+\lambda_{i-1}N_{i-1}$}
{wiki}
The Bateman equation gives the populations in a sequential <radioactive decay> chain. For a parent with population $N_1(0)$ and an initially absent daughter, distinct decay constants give $N_2(t)=N_1(0)\lambda_1(e^{-\lambda_1t}-e^{-\lambda_2t})/(\lambda_2-\lambda_1)$; the first population satisfies $N_1'=-\lambda_1N_1$.