Attempts to Confirm the Existence of the 10-Minute Isotope of102

Abstract

In many score of experiments conducted in various ways over a period of many months they find that they are unable to confirm the element 102 discovery work of Fields et al. reported in 1957. These experimenters ascribed to an isotope of element 102 an alpha particle activity having an energy of 8.5 {+-} 0.1 Mev and a half-life of approximately 10 minutes. It was reported to be produced by bombardments of a 1 mg/cm{sup 2} curium target with 0.03-0.10 mter-microamperes of C{sup 13} ions of about 90 Mev energy in the internal beam of the Nobel Institute 225 cm cyclotron. Our attempts to reproduce this activity were made with the monoenergetic ion beam available from the Berkeley heavy ion linear accelerator (HILAC). Curium with a similar isotopic composition was used, except that instead of one target they used six separate electroplated targets, four with 0.4 mg/cm{sup 2} curium and two with 0.1 mg/cm{sup 2} curium. These were mounted in vacuum so that the heavy ion beam could pass through and knock the transmutation recoils into 0.9 mg/cm{sup 2} palladium foils. After a suitable bombardment the six catcher foils were dissolved in a few drops of concentrated aqua regia and an actinide element fraction quickly separated from palladium by elution with 2M HCl from a column packed with Dowex-1 anion exchange resin. It was possible to examine a trans-plutonium fraction within 8 minutes from the end of bombardment. A wide range of energies (60-100 Mev) of both C{sup 12} and C{sup 13} projectiles and (+6) ion currents up to 0.2 microamperes were used. In order to compare these bombardments with those which were reported to have produced the 8.5 Mev alpha activity one can compare the amounts of the other alpha particle activities that are produced in such bombardments. The nuclides Fm{sup 250}, Cf{sup 245}, Cr{sup 244}, and Cf{sup 246} were found in far greater amount in the experiments than in the aforementioned cyclotron runs. In the case of Cf{sup 246}, for example, which is produced with a relatively flat excitation function they found in a typical experiment about 40 alpha counts per minute. This should be compared with 0.1 alpha counts per minute of Cf{sup 246} found in the cyclotron experiment which was reported to have yielded four 8.5 Mev events.