Evidence for Doubly Charged Negative Fluorine Ions from Electron Bombardment of CF3Cl

Abstract

MULTIPLY charged negative ions are important because of their potential use in tandem accelerators. In such machines the ions are first accelerated as negative ions and then stripped to a multiply charged positive species which is further accelerated. Stuckey and Kiser1 have reported the observation of doubly charged negative ions of oxygen and the halogens using an omegatron for mass analysis. Since early theoretical analysis2 indicated that the lifetimes for such species would be less than 10−9 s and Fremlin3 pointed out that there may be alternative explanations of the omegatron observations, there has been doubt about the actual existence of multiply charged negative ions. More recently Baumann et al.,4 using a Penning ionization source and a 60° magnetic sector instrument for mass analysis, observed some peaks which correspond to a mass half of the negative ion X−. This peak could be due to X2− or it could be a metastable peak due to the dissociation of X2−⇐X−+X before reaching the analysing magnet. To distinguish between these processes they used a stage of electrostatic deflexion for the beam as it left the magnetic sector and definitely established the existence of X2− in several elements.