Positive identification of XeH^- molecular ion

We describe in the present work the observation of XeH^- molecular ions from a standard Hiconex 834 source in which a sputter target of AgI mixed with Ag was sprayed with Xe gas. The formation of XeH^- ions is positively demonstrated by identifying ¹²⁹Xe and ¹³¹Xe by AMS analysis and energy and time-of-flight measurements, when negative ions of mass 130 and 132, respectively, are injected into the 14UD Rehovot Pelletron tandem accelerator. No evidence for the formation of Xe^- ions was found. The dependence of the intensity of the xenon group on the xenon gas pressure in the ion source shows that the probability of formation of XeH^- is very low and should not pose a significant background problem under normal circumstances in AMS measurements of ¹²⁹I.