Superelastic electron scattering within a magnetic angle changer: determination of the angular momentum transferred during electron excitation over all scattering angles

By utilising super-elastic electron scattering from laser excited atoms together with a new Magnetic Angle Changing device, it is possible to determine the differential cross sections for excitation of atoms by electron impact over the complete scattering geometry. In the experiments described here, these techniques are combined to reveal the angular momentum transferred to calcium atoms during electron excitation to the 4¹P₁ state, from near zero degrees to beyond 180 degrees for the first time. The results significantly extend all previous data, and are compared to calculations based on a distorted wave Born approximation by Stauffer and colleagues. The experimental techniques are discussed, and results are presented for electron energies of 45eV and 55eV.