Total cross sections for the production of slow heavy negative ions and of free electrons in collisions of O2−, O−, OH−, and H− ions with O2 molecules have been measured over the primary-ion KE range from a few electron volts to 350 eV. The experiments are of the ion-beam gas-scattering type and utilize a radio-frequency filter to give separately the currents of detached electrons and slow product negative ions. The cross sections for slow ion formation, σt, were appreciable at all energies studied, for all four collision systems. The dominant contributions to σt could in most cases be attributed to simple charge transfer, although in the H−–O2 and OH−–O2 systems at low energies, the data indicate that ion–molecule reactions also contribute. With exception of the H−–O2 system, the electron detachment cross sections were similar in magnitude and in behavior with collision energy to those which have been measured previously for other systems.

An improved apparatus for the production of beams of negative ions and the measurement of the elastic and inelastic scattering of negative ions in gases at low pressures in briefly described. The measured cross-sections are given for the scattering of 4—400 ev H— ions in hydrogen. In the range 4—40 ev (1.1—1.8 A) the interaction potential derived from the elastic scattering is V (ev) = —4.64×10—32/r4 (r in cm) which is close to the theoretical polarization interaction. The inelastic scattering is presumed to be due to electron detachment. The inelastic cross section increases from 1 cm—1 at 7 ev to 8.7 cm—1 at 395 ev. Above 75 ev the measured elastic cross section increases with increasing ion energy. This is attributed to the appearance of inelastic collisions which result in electronic excitation of the hydrogen molecules.

No abstract

No abstract

The negative ions formed by electron bombardment in water vapor and in a mixture of water and hydrogen peroxide vapors have been investigated in a mass spectrometer. The principal ions found with water vapor in the ion source are H~, 0~and OH-. With the addition of a small amount of hydrogen peroxide vapor, Oí -and ,ions are also found at relatively high intensity. No H2O2-(or 0-H20) ions were observed in either case. Data are presented to show that the OHion is formed in a secondary collision between Hand H20. Measurements of the total scattering cross-sections for 350 e.v. O,and O2H-ions in oxygen have been made. It is shown from these measurements that the ions of mass 32 obtained by the electron bombardment of oxygen are the same as those obtained from the H2O-H2O2 vapor. The utility of the scattering technique for the identification of gaseous ions is discussed.