Ratio of1s−2sand1s−2pExcitation of Atomic Hydrogen by Electron Impact

The electron-photon coincidence technique is used to separate the 54.4-eV electron impact $2p$ and $2s$ excitation cross sections of atomic hydrogen. The $\frac{2s}{2p}$ cross-section ratios, normalized to theory at 10°, are in excellent agreement with the close-coupling calculations of Kingston, Fon, and Burke, in reasonable agreement with hybrid pseudostate close-coupling plus unitarized Born calculations, but in strong disagreement with the distorted-wave Born-approximation and hybrid close-coupling plus distorted-wave polarized-orbital calculations.