On the Mean Lifetime of Metastable Neon Atoms

Penning has shown that illumination of the Townsend discharge in neon with red light from an auxiliary neon arc reduces the number of excited atoms in the former. The concentration of excited atoms in the Townsend discharge as a function of illumination intensity can be computed from the electronic properties of neon; a comparison with Penning's direct measurements evaluates the mean lifetimes of both the metastable and the resonance states in the gas. The numerical results for 36 mm pressure are: mean lifetime in sec. of the ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ metastable $\mathrm{state}=2\mathrm{}\times \frac{{10}^{-3\mathrm{}}}{p}$; of the $2{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ resonance $\mathrm{state}=4\mathrm{}\times \frac{{10}^{-5\mathrm{}}}{p}$, where $p$ is the pressure in mm Hg. Values for the mean lifetime of the $2{}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ state derived by Zemansky's method from absorption measurements at about 3 mm Hg pressure are: $9\times \frac{{10}^{-4\mathrm{}}}{p}$ from Meissner and Graffunder's measurements, and $8\times \frac{{10}^{-3\mathrm{}}}{p}$ from Dorgelo and Washington.