Small-angle (e−, Na) scattering in the 6-25-eV range

We have investigated elastic and inelastic scattering of electrons by sodium atoms at intermediate energies (6-25 eV) by the atomic-recoil technique, using a new atomic-beams apparatus. The effects of the apparatus geometry, atomic velocity, and electron energy distributions on the analysis of the experimental results have been examined in detail, and their effects on small-angle scattering have been incorporated into the present work. We present absolute measurements of the elastic ($e^{-}$, Na) differential cross section at 10 eV for electron polar angles ranging between 12° and 22°. These measurements are in good agreement with the normalized results of S. K. Srivastava and L. Vuskovic [J. Phys. B 13, 2633 (1980)] and in reasonable agreement with the two-state close-coupling calculation of M. R. Issa (Ph.D. theis, University of Durham, 1977). We also present absolute measurements of an integral over small angles of the $3{}_{}{}^2{}_{}{}^{}P$ impact-excitation differential cross section, together with a precise prescription for comparison with theory. We found that the distortedwave-polarized-orbital calculation of J. V. Kennedy, V. P. Myerscough, and M. R. C. McDowell [J. Phys. B 10 3759 (1977)] gives results which are too high in the forward direction, while those of Issa are somewhat low.