Difference method for the measurement of the excited-state lifetime

A description is given of a new method for measuring the excited-state lifetime τ, which can be used when τ is substantially shorter than the exciting pulse duration. The method essentially involves determining experimentally the difference between the fluorescence and exciting pulse durations and comparing this with the theoretical value. The method can be used to measure subnanosecond fluorescence-level lifetimes, using an apparatus having a nanosecond temporal resolution. The experimentally measured lifetime τ = 85 psec for an aqueous solution of erythrosine agrees with the published data.