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Measurements have been made on the gross-ionization cross sections for 0.1–20-keV electrons on water vapor at pressures of about 3×10−4 torr. The results are compared with the cross sections of H2 and O2. Within the experimental error of 15% we found no deviations from the additivity rule. The energy dependence of the cross section satisfies the Bethe—Fano—Platzman relation for collision-induced dipole transitions at energies exceeding 400 eV. A comparison is made with photoionization and inelastic electron-scattering cross sections. Some results are given on the partial cross sections for the production of fragment ions for 0.02–2-keV electrons on water vapor.

The systems germanium-graphite and germanium-silicon-carbon have been studied. Several gaseous molecules containing Ge, Si, and/or C were observed and their dissociation energies determined from measured partial pressures. A general picture of the dissociation energies of di-, tri-, and tetraatomic intergroup IVB molecules is deduced from these measurements. Incidental to this study the vapor pressure of pure Si was determined; the result confirms the heat of sublimation obtained previously.

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