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 Xe-129 and Xe-131 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 I-129.