Abstract The half-width of Doppler broadening is derived without assuming Maxwell's distribution for the velocities of the radiating atoms. In the absence of Doppler broadening there is only natural radiation broadening, and by thermalizing the asymptotic Cauchy distribution one obtains asymp-totic double exponential distributions for the largest (blue) and smallest (red) values of the frequency shift. These are the relevant extreme value distributions for largest and smallest values. Since the mean values are opposite and equal there is a zero shift in the line, while the standard deviation gives an expression for the half-width to within 2% of the Doppler half-width obtained from the Maxwellian when the damping coefficient is taken as the ratio of the natural radiation damping coefficient to the fine structure constant.
The theories of absorption in mercury vapor of mercury resonance light of wave-length 2536.7A as formulated by Malinowski and H. A. Wilson are briefly reviewed. It is well established that the absorption coefficient for resonance radiation increases as the number of absorbing atoms decreases. This is probably due to a Doppler effect in the radiating vapor. To diminish the influence of the Doppler effect a jet of mercury vapor was used, and the resonance radiation coming from it was investigated. A series of measurements of the absorption coefficient of this light is given. The maximum atomic absorption coefficient observed is 10.22\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$, nine times as large as any previously observed. It is shown that Malinowski's assumptions are not in accord with the observed effects.