The Mechanism of the Positive Column in Mercury Vapor at Intermediate Pressures

Calculations based on the radiant intensity for the principal spectral lines of 4-ampere mercury arcs at 450 mm and 500 mm (Hg) pressure, indicate for low quantum states a dynamic equilibrium with electrons at approximately 6000^∘{}K, the temperature indicated by the absolute spectral intensity for three reversed lines. For high quantum states differing only in total quantum number, there appears to be a tendency toward Boltzmann equilibrium due to collision with normal atoms at approximately the temperature (2500^∘{}K) calculated from the heat balance by Langmuir's theory of conduction and convection in gases. This agrees with predictions from the principle of spectroscopic stability.