Angle and Channel Dependence of Resonances ine-He Scattering near 60 eV

Abstract

The ${\mathrm{He}}^{-}$ resonances at 57.1 and 58.2 eV in the electron scattering from He were studied as a function of angle in three inelastic channels corresponding to excitation of the $\mathrm{}\left(1s2s\right)\mathrm{}{}_{}{}^3{}_{}{}^{}S$, $\mathrm{}\left(1s2s\right)\mathrm{}{}_{}{}^1{}_{}{}^{}S$, and $\mathrm{}\left(1s2p\right)\mathrm{}{}_{}{}^1{}_{}{}^{}P$ states of He. The line shapes of the resonances are found to vary with angle. The application of the Fano-Cooper formula, developed for the case of photon absorption, to resonances in inelastic electron scattering is discussed, along with a simple procedure for determining the line profile indices. The angular dependence of the ${}_{}{}^1{}_{}{}^{}S$, ${}_{}{}^3{}_{}{}^{}S$, and ${}_{}{}^1{}_{}{}^{}P$ excitations at 56.5 eV was also measured out to about 60°.