Abstract
Using the Argonne 100-in.-radius double-focusing mass spectrometer we have searched for long-lived (> or =10/sup -5/ sec) doubly charged atomic negative ions with the use of electron impact and Penning ionization sources. Our source operating conditions are similar to those of previous experiments which claim the existence of such ions. In contrast to all previous experiments, our mass resolution is sufficient to absolutely identify any impurity ion from its mass defect, and the machine design is such that artifact peaks (Aston peaks), caused by collisional dissociation of molecular negative ions, do not occur. Using a variety of target gases, we set upper limits for the production of doubly charged or singly charged species in electron bombardment and Penning sources of X/sup 2 -/ to X/sup -/< or =10/sup -7/ to 10/sup -8/ and X/sup 2 -/ to X/sup -/< or =5 x 10/sup -10/, respectively. These results contrast to those of previous experiments which claim positively identified ratios of X/sup 2 -/ to X/sup -/ = 10/sup -1/ to 10/sup -2/ and X/sup 2 -/ to X/sup -/roughly-equal10/sup -3/, respectively. We find no evidence of any doubly charged atomic negative ion.
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