Electron impact differential and integral cross sections for excitation of the n = 2 states of helium at 29.2 eV, 39.2 eV and 48.2 eV

Abstract

A high resolution electron impact spectrometer using electrostatic monochromators and the cross-beam technique is described. Considerations related to its constraction and use in measuring cross sections are discussed. This instrament was used to obtain absolute values for differential and integral excitation cross sections of the n = 2 manifold states of helium at 29.2 eV, 39.2 eV and 48.2 eV. The results are presented and compared with currently available theoretical calculations. (auth)