Large-angle electron-photon coincidence experiment in atomic hydrogen

Abstract
1s2p excitation in hydrogen has been studied by observing the angular correlation of Lyman α photons detected in coincidence with inelastically scattered electrons at 54.4 eV incident energy. The electron scattering angles ranged from 10° to 133°; the results at scattering angles larger than 20° cannot be explained by currently available theories.