The Absorption Coefficient for Slow Electrons in Gases

The absorption coefficient has been measured in ${\mathrm{H}}_2$, He, A, Ne, ${\mathrm{N}}_2$, and CO for electrons with velocities corresponding to from 0.5 to 400 volts. As a result of the high resolving power of the apparatus fine structure was found in the curves of all the gases. A minimum in the absorption coefficient curve was found in every case at velocities between 0.7 and 1.1 ${\mathrm{}\left(\mathrm{volts}\right)\mathrm{}}^{1/2}$. A lack of agreement between the present measurements at velocities below 2 volts and recent results of Ramsauer and Kollath appears to be due to a difference of about 0.5 volts in the velocity scales of the two sets of observations.