Precise determination of differential electron scattering cross sections. I. The apparatus and the N2 results

Abstract

Total (elastic plus inelastic) differential cross sections of 30, 40, and 50 keV electrons incident on N₂ have been measured in the angular range of 9–200 mrad. The accuracy achieved was about 0.1%. The apparatus is discussed in extensive detail. The data are used to determine the molecular structure parameters and then matched to the independent atom model composed of Hartree–Fock atoms. In a second comparison, configuration interaction atoms are utilized. The difference curve of s⁴(I_expt−I_theo) is constructed and integrated in order to determine the molecular binding energy. The value varies from 17 eV to 10 eV depending on the matching procedure chosen. Since the cross sections were measured at various incident electron energies, the validity of the first Born approximation could be investigated. It was found that the Born theory holds to within the uncertainty in the data. Thus, recent discrepancies found in Compton profile measurements must be attributed to a failure of the binary encounter theory.