these values are of the same order of magnitude as the value observed for the ionization potential in helium,
assume[31], and the value for the frequency of the ultra-violet absorption in helium determined by experiments on dispersion
[32].
The frequency in question may be regarded as corresponding to vibrations in the plane of the ring (see [p. 30]). The frequency of vibration of the whole ring perpendicular to the plane, calculated in the ordinary way (see [p. 32]), is given by
. The fact that the latter frequency is great compared with that observed might explain that the number of electrons in a helium atom, calculated by help of Drude’s theory from the experiments on dispersion, is only about two-thirds of the number to be expected. (Using
the value calculated is