Angular correlation study of H(2p) excitation by electron impact

Excitation of the 2p state of hydrogen by 54.4 eV electrons is studied experimentally using the scattered electron-decay photon angular correlation technique. At small scattering angles previous experimental results and a range of theoretical calculations are confirmed. At large scattering angles, the present data consistently support these theoretical models but do not agree with previous angular correlation data at this energy. This fundamental discrepancy between experiment and theory for the simplest electron excitation process in the simplest atom is therefore resolved in favour of theory.