Observations of Negative Ions in Oxygen and Water Vapor by Ion Cyclotron Resonance

Observations were made of the cyclotron resonance absorption of O—, O2—, H—, OH—, and H2O— in oxygen containing water vapor. A technique utilizing a circularly polarized rf electric field is described which allows the cyclotron resonance absorptions of negative and positive ions to be distinguished. The production of O2— was found to depend on the presence of water vapor as well as oxygen and is probably due to charge exchange with H—.