Angular and energy dependence of cross sections for ejection of electrons from water vapor. I. 50-2000-eV electron impact.

We have measured the angular and energy distribution of the absolute cross sections for ejection of electrons from water vapor by electrons incident at 50--2000 eV. The angular range was 15/sup 0/ to 150/sup 0/ and the range of secondary electron energies was from 2 eV to an energy equal to the primary energy minus the first ionization potential. Electron energies were analyzed with a parallel-plate electrostatic analyzer with a resolution of 1.1%. Generally good agreement is obtained with the data of Opal et al. (J. Chem. Phys. 55, 4100 (1971)) at 500 eV except at the extremes of their angular range. Our energy distributions are compared to various binary-encounter-model calculations.