Angular distribution of electrons elastically scattered from hydrogen atoms. II

We have measured absolute differential cross sections of atomic hydrogen by electron impact. A modulated crossed-beam method was used. The energy and angular range measured were from 40 to 200 eV and from 12 degree to 156 degree, respectively. Atomic hydrogen was generated by a microwave discharge device. The present results were compared with the previous measurement by Williams [J. Phys. B 8, 1683 (1975); 8, 2191 (1975)] and a few theoretical results. There is relatively good agreement in the forward scattering, but a signficant discrepancy has been found in the extreme backward direction in this energy region. In general, the present results are larger than the previous measurement and theoretical results by more than a factor of 3 at extreme angles. The present results of the integrated cross sections are in good agreement with the previous measurement and theoretical predictions, even though there are disagreements in the backward scattering due to the very small differential cross sections in the backward angles