MOMENTUM-TRANSFER DEPENDENCE OF THE LYMAN-BIRGE-HOPFIELD AND THE K-SHELL PREIONIZATION LINES IN THE NITROGEN MOLECULE BY MEANS OF HIGH-ENERGY ELECTRON-IMPACT SPECTROSCOPY

The generalized-oscillator-strength (GOS) distribution for the Lyman-Birge-Hopfield (LBH) and the K-shell preionization lines in the nitrogen molecule, obtained with electron impact energies of 25-28 keV, are reported for the momentum-transfer range of 0.5-3.1 a.u. The results for the LBH were found to be in agreement with previously published low-energy experiments and also the most recent theoretical predictions. Possible reasons for problems encountered in previous high-energy electron spectroscopic experiments are discussed. The results for the preionization line confirm the measurements of Camilloni et al. [J. Phys. B 20, 1839 (1987)] and agree with the theory presented in the following paper [Bielschowsky, Nascimento, and Hollauer, Phys. Rev. A 45, 7942 (1992)]. The reliability of the results presented here can in part be judged by the quality of the optical-oscillator-strength distribution obtained by extrapolatin the GOS to zero momentum transfer.