Measurement of Differential Cross Sections of Low-Energy Electrons Elastically Scattered by Gas Molecules. I. Apparatus

Abstract

An electron diffractometer designed for the study of elastic scattering of a low-energy electron beam by a flow of gas molecules emitted from a fine nozzle is constructed. As a check of the accuracy of the measurement, relative differential cross sections for the nitrogen molecule are measured with the angular precision and resolution of about 0.3° and less than 1°, respectively. The angular distributions of the scattered electrons, measured from 4° to 150°, agree within 5% (in the relative scale) with those measured by Bromberg in the range from 5° to 110° at the incident electron energies of 300 eV and 500 eV in spite of the differences in the techniques. Similar measurements made for 100 and 50 eV electrons show minimum cross sections at about 90°.