The Scattering of Electrons from RaE by Thin Metal Foils

Beta-rays from radium E of energy greater than 0.2 Mev were scattered by thin foils of metal and the distribution of the scattered electrons was measured with a Geiger-Müller counter between the angles 0° and 45°. Two thicknesses each of aluminum, copper, silver, and gold foils were used as the scattering material. The thinner set of foils was made of thickness such that each had the same cross section for single scattering, that is, $Z^2\mathrm{nt}$ was kept constant, while the second set of foils was made twice as thick. The Wentzel angle was 22° for the first set and 33° for the second. A comparison of the experimental results with the Mott theory in the range above the Wentzel angle was made by integrating over the energy spectrum of the radium E source used. For the energy and angular ranges investigated, it is concluded that such deviations from the Mott formula which exceed experimental error are due to the effects of multiple scattering and the inadequacy of the Wentzel criterion for elements of small $Z$. The check in absolute magnitude of the scattering is considered satisfactory.