Decay Constant
The probability per unit time that an individual radioactive nucleus will undergo spontaneous nuclear decay.
Governing formula
λ = -(1 / N) (dN / dt) = ln(2) / t_½
SI unit
s⁻¹ or years⁻¹
In depth
The decay constant λ is a constant characteristic of a specific radionuclide species. Activity A = λ N represents the instantaneous rate of nuclear decays per second in a sample.
Examples in the real world
Calculating the decay constant of Radon-222 (λ ≈ 2.1 × 10⁻⁶ s⁻¹) from its 3.82-day half-life.