Doubly charged Negative Ions of Oxygen, Fluorine, Chlorine and Bromine

Abstract

ELECTRON impact processes give rise to both positive and negative ions. The negative ions are, in general, only about 10−3 times as intense as the positive ions. In contrast with positive ions, only singly charged negative ions have previously been reported. Calculations involving the crystalline state, where doubly charged negative ions (such as O = and S =) apparently do exist, indicate that the formation of O = from O − requires 7.8 eV in the gas phase1. The lifetime of a doubly charged ion in the gas phase would be expected to be short and has been predicted to be 10−10 sec or less2—too short for observation in the usual mass spectrometer. This communication reports the observation of doubly charged negative ions of oxygen, fluorine, chlorine and bromine, with indications that the lifetimes are of the order of 10−4 sec (the ion collection time in the mass spectrometer used).