https://doi.org/10.1351/goldbook.L03516
The time required for the @L03641@ intensity to decay from some initial value to \(\frac{1}{\text{e}}\) of that value (\(\text{e} = 2.718\,...\)). Lifetimes can be measured by @P04529@ (@F02416@) where the phase shift between the sinusoidally modulated exciting light and the emitted light is measured.