Search for long-lived doubly charged negative atomic ions

We have searched for long-lived (≳${10}^{\mathrm{-}5}$ s) doubly charged negative atomic ions produced in a high-current cesium sputter source with a tandem-accelerator-based charge spectrometer. The results of these ultrasensitive searches for doubly charged negative atomic ions of group VI B and VIII B elements, and hydrogen that can survive the acceleration to the tandem terminal, are reported. No evidence of doubly charged negative atomic ions was observed, and upper limits for the ratio of production (and survival) of doubly charged to singly charged negative atomic ions were obtained for the cesium sputter source.