The Diffusion of Metastable Atoms in Mercury Vapor

The diffusion of metastable atoms in mercury vapor was studied with a four-electrode tube of special construction, and with short voltage pulses separated by variable time intervals actuating the accelerating and photo-electric gauzes. The change in the rate of arrival of metastable atoms at the outer boundary of a spherical volume of gas was determined as a function of the time elapsed after a number of atoms had been formed at the center. Observations were made at vapor pressures ranging from 3×${10}^{-9\mathrm{}}$mm to 0.33 mm. A comparison of the experimental results with the theoretical values for normal mercury atoms under the same conditions shows that the assumptions made by Webb and Messenger that metastable mercury atoms travel across the experimental tube and produce a direct action upon the "photo-electric" plate is correct. It is also found that the effective radius of the metastable mercury atom is about 1.5 times as large as that of the normal atom, and that metastable and normal mercury atoms obey the same general laws of diffusion. Evidence of the loss of energy of excitation as the result of collision between normal and metastable mercury atoms was found.