Lifetimes of the upper states of two optical-resonance transitions in aluminum have been measured using the phase-shift method. Data were taken over a large range of fluorescence intensities, to allow for evaluation of the effects of scattered exciting light and radiation entrapment. The results obtained are τ4s2S½= 7.05 ± 0.30 nsec, τ3d2D= 13.70±0.40 nsec.
PAUL T. CUNNINGHAM, "Lifetime Measurements of the 4s2S½ and 3d2D States of Aluminum by the Phase-Shift Method," J. Opt. Soc. Am. 58, 1507-1509 (1968)