Bethe surface, elastic and inelastic differential cross sections, Compton profile, and binding effects for H2 obtained by electron scattering with 25 keV incident electrons

Abstract

Electron impact spectra for H2 have been obtained at scattering angles of 1°, 1.5°, 2°, 3°, 4°, 5°, 7°, and 10° using 25 keV incident electrons. The measured intensities were converted to generalized oscillator strengths and placed on an absolute scale at each scattering angle by the use of the Bethe sum rule for the generalized oscillator strength distribution. The cross section differential with respect to both solid angle and energy loss of the scattered electron was corrected for relativistic and exchange effects and integrated over energy loss to obtain the inelastic differential cross sections. In addition the elastic cross section differential with respect to solid angle was measured. The results are all in excellent agreement with theoretical calculations. The total elastic cross section was determined using additional data from another source. The Compton profile was determined from the 7° scattering data and was found to agree well with the previous x-ray results. Consistent generalized optical sums (2,1, − 1, − 2) and optical sum inequalities for the generalized oscillator strength were also obtained. In addition inelastic scattering factors were computed from the (−1) optical sum and were found to agree well with available theory. Chemical binding effects were explored using electron density difference functions obtained from the differential cross sections. For the first time the intensity difference functions for the elastic and inelastic scattering were determined separately. It is argued that the experimental method used in this study to obtain the intensity difference functions represents the best approach so far developed for obtaining direct information about molecular real space charge densities.