Radiance Lifetimes in the Resonance Series of Ar I.

Radiative lifetimes of the six lowest-energy $J=1\mathrm{}$ levels of Ar I have been measured using a pulsed electron technique. The wavelengths and measured lifetimes in nanoseconds are 1066.66, 8.60 ± 0.4; 1048.22, 2.15 ± 0.2; 879.95, 10.1 ± 0.4; 876.06, 3.48 ± 0.2; 869.75, 17.5 ± 2.0; 966.8, 3.0 ± 0.4; where the error estimates are roughly a factor of 10 larger than the statistical errors. Estimates of branching ratios are made where necessary and $f$ values for the above transitions are given. Lifetimes of cascading levels estimated with a two exponential fit are consistent with known lifetimes of Ar I visible lines. Extrapolation to zero pressure to account for photon entrapment was made for lifetimes enlarged less than 30%.