RADIUM, ACTINIDES, AND THEIR MOLECULAR NEGATIVE-IONS FROM A CESIUM SPUTTER ION-SOURCE

The negative ions of the isotopes Ra-226, Pa-231 and Pu-244, produced by a Cs sputter ion source, have been observed for the first time using the IsoTrace heavy element AMS system. The properties of these negative ions have been compared with those of Th and U, and the electron affinities of all these elements (Ra, Th, Pa, Th and Pu) have been found to be similar and greater than 50 meV. Some molecular negative ions of these elements, in particular carbides and oxides, have also been measured. It was found that di-carbide is generally a profitable molecule form for measuring Ra, Th and Pa, while mono-oxide is more efficient for measuring U and Pu.