Angular distributions of electrons elastically scattered fromH2

Abstract

Angular distributions of electrons elastically scattered from ${\mathrm{H}}_2$ have been measured by a crossed-beam method. Energy and angular range covered were from 2.0 to 200 eV and from -96° to + 156°, respectively. Comparison has been made with the previous measurements and theories. There is a good agreement above 100-eV incident energy between the previous measurements and theories and the present results, but below 100 eV considerable discrepancies exist between the previously reported results and the present measurements in the shape as well as in the magnitude of the angular distribution. The total cross sections of Golden et al. [D. E. Golden, H. W. Bandel, and J. A. Salerno, Phys. Rev. 146, 40 (1966)] above 7 eV are smaller than the present results (pure elastic) by as much as 24%, and the results of Srivastava et al. [S. K. Srivastava, A. Chutjian, and S. Trajmar, J. Chem. Phys. 63, 2659 (1975)] are also smaller than the present results by as much as 15%. The momentum-transfer cross section calculated directly from the present results of angular distribution show good agreement with those results derived from transport coefficients is swarm experiments by Frost and Phelps [L. S. Frost and A. V. Phelps, Phys. Rev. 127, 1621 (1962)] and Crompton et al. [R. W. Crompton, D. K. Gibson, and A. I. McIntosh, Aust. J. Phys. 22, 715 (1969)] below 7 eV, but not for results above 7 eV. The results of Srivastava et al. are in agreement within the experimental uncertainties above 10 eV.