Electron scattering from H 2 O : Elastic scattering

Differential cross sections for elastic electron scattering from gaseous water are reported. The measurements are obtained using the relative flow method with He as the standard gas and a thin collimating aperture source of gas instead of a conventional needle source. Differential cross sections were measured at incident energies of 1, 2, 4, 6, 8, 10, 15, 20, 30, 50, and $100\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for scattering angles ranging from 5\ifmmode^\circ\else\textdegree\fi{} to 130\ifmmode^\circ\else\textdegree\fi{} and integrated over angles to obtain integral cross sections. Corresponding calculations of the differential cross section are carried out using the Schwinger multichannel method, employing extensive basis sets and considering polarization and dipole-scattering effects. Whereas excellent qualitative agreement with past measurements of differential cross sections is observed, our measurements are found to be consistently in significant quantitative disagreement with these measurements. The present calculations, on the other hand, generally agree in magnitude with previous results.