The Absorption Coefficient for Slow Electrons in Cadmium and Zinc Vapors

Abstract

The variation with the electron velocity of the absorption coefficient, $\ensuremath{\alpha}$, or the effective collision cross-section has been measured in the vapors of cadmium and zinc and found to follow a curve of the type previously found for mercury. The cadmium curve has a maximum at about 40 volts, $\ensuremath{\alpha}=130$, and a minimum at about 25 volts, $\ensuremath{\alpha}=126$, followed by a steady rise with decreasing velocity to the limit of accurate measurements, 1 volt, $\ensuremath{\alpha}=300$. The zinc curve has a very flat maximum at about 50 volts, $\ensuremath{\alpha}=76$, a minimum at about 36 volts, $\ensuremath{\alpha}=74$, followed by a steady rise to $\ensuremath{\alpha}=500$ at 1 volt. The magnitudes of the maximums are in the order: Cd, $\ensuremath{\alpha}=130$; Zn, $\ensuremath{\alpha}=75$; and Hg, $\ensuremath{\alpha}=60$. Other related properties of these atoms, such as the molar refractivity and the critical potentials, show this same irregularity in order.