Excitation of the $2p$ state of atomic hydrogen by electron impact was studied using the electron-photon angular correlation technique with the aim of resolving a long-standing and serious discrepancy between theories and previous experiments at large scattering angles. At a scattering angle of 100°, where the discrepancy was greatest, the present result shows excellent agreement with the theoretically predicted correlations.

• Received 11 July 1997

DOI:https://doi.org/10.1103/PhysRevLett.79.2951