Elastic electron scattering from water vapor and ice at high momentum transfer.

ABSTRACT

We compare the area, peak separation, and width of the H and O elastic peak for light and heavy water, as observed in spectra of keV electrons scattered over large angles. Peak separation is well reproduced by the theory, but the OH area ratio is somewhat larger than expected and is equal to the OD area ratio. Thus no anomalous scattering from H was observed. Only minor differences are observed for scattering from a gaseous or a solid target. The extracted mean kinetic energy of H and D agreed within 5% with the calculated ones for ice. For the more difficult vapor measurements agreement was on a 12% level. A preliminary attempt to extract the O kinetic energy in ice agreed within 10% with the calculated values.