The Absorption Coefficient for Slow Electrons in Cadmium and Zinc Vapors

The variation with the electron velocity of the absorption coefficient, α, 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, α=130, and a minimum at about 25 volts, α=126, followed by a steady rise with decreasing velocity to the limit of accurate measurements, 1 volt, α=300. The zinc curve has a very flat maximum at about 50 volts, α=76, a minimum at about 36 volts, α=74, followed by a steady rise to α=500 at 1 volt. The magnitudes of the maximums are in the order: Cd, α=130; Zn, α=75; and Hg, α=60. Other related properties of these atoms, such as the molar refractivity and the critical potentials, show this same irregularity in order.