Mean Lives of Mercury Linesλ2537andλ1849

Abstract

The mean life of the mercury line $\lambda 2537$ was measured by the alternating voltage method previously described by Webb. The radiation was excited in a quartz tube by impact with electrons from a hot cathode. The photoelectric system was contained in a separate tube also of quartz. The photoelectric surface was zinc evaporated on a nickel plate. Measurements of the apparent life were made with diminishing mercury vapor pressures until further reduction of pressure produced no change in the measured rate of decay of the radiation. At these low pressures (below 3×${10}^{-4\mathrm{}}$ mm, for the geometry used) the absorption and reemission of the radiation was negligible and the true life of a single excitation process was measured. This was found to be 1.08×${10}^{-7\mathrm{}}$ sec. with an estimated precision of one percent.