e-H Resonances in the2pExcitation Channel

Abstract

The cross section for the electron-impact excitation of the hydrogen atom to the $2p$ radiative state has been measured from the threshold (at 10.2 eV) to 50 eV. Primary interest is given to the region between the threshold and the $n=4\mathrm{}$ level of the hydrogen atom, where several resonances have been identified. An electron-beam resolution of 0.07 eV has been used to study the resonances, while a resolution of 0.18 eV has been used to determine the general behavior of the cross section. Below $n=3\mathrm{}$ the ${}_{}{}^1{}_{}{}^{}S$ resonances appear to agree with the theoretical predictions, but in the case of the higher angular-momentum ${}_{}{}^1{}_{}{}^{}D$ resonance, the agreement between present theory and experiment is poor. Balmer-$\alpha$ excitation is discussed.