The "Decay Constant" is the proportionality between the size of a population of radioactive atoms and the rate at which the population decreases because of radioactive decay.
Applicable units are those of quantitykind:DecayConstant
http://en.wikipedia.org/wiki/Exponential_decay
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The "Decay Constant" is the proportionality between the size of a population of radioactive atoms and the rate at which the population decreases because of radioactive decay.
Relative variation $\frac{dN}{N}$ of the number $N$ of atoms or nuclei in a system, due to spontaneous emission from these atoms or nuclei during an infinitesimal time interval, divided by its duration $dt$, thus $\lambda = -\frac{1}{N}\frac{dN}{dt}$.
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