Ultraviolet Photons in the Decay of Metastable Argon Atoms

Abstract

Some measurements of the lifetime of uv photons emitted by the excited states of argon are reported, when the excitation is obtained by the impact of the electrons in a Townsend avalanche. The measurements were made by converting the ultraviolet into visible light by means of a fluorescent screen and by observing the visible light with a photomultiplier. The results are that the energy of the uv photons is about 10 ev and that the law of emission in time is represented by the formula $\exp -\frac{t}{{\tau }_A}-\exp -\frac{t}{{\tau }_M}$, where ${\tau }_A=3.4\mathrm{}\times {10}^{-6\mathrm{}}$ sec and ${\tau }_M=\frac{1}{9p^2}$ sec ($p=\mathrm{gas}\mathrm{pressure}\mathrm{in}\mathrm{mm}\mathrm{Hg}$).