Serial reaction dwell-time density
= Serial reaction dwell-time density
{title2=$p(t)=k_1k_2(e^{-k_1t}-e^{-k_2t})/(k_2-k_1)$}
Two sequential independent memoryless reaction waits have a <hypoexponential distribution>. Convolution gives $p(t)=k_1k_2(e^{-k_1t}-e^{-k_2t})/(k_2-k_1)$. Equal rates give the <Erlang distribution> $k^2te^{-kt}$. A nonzero mode distinguishes this ideal two-event model from a single exponential wait, but does not chemically identify the events.