A search for superheavy elements with half-lives between a few minutes and several hundred days, produced in the 48Ca+ 248Cm reaction

Abstract

The results of recent unsuccessful attempts to synthesize and identify superheavy elements at the Lawrence Berkeley Laboratory SuperHILAC are described. A thin 248Cm target was irradiated with 48Ca ions at an average energy in the target of 255 MeV. Direct counting of thin recoil foils for short-lived spontaneous fission activity was done. Two long irradiations were also made and radiochemical group separations for the superheavy elements were carried out. In the first radiochemical experiment, a thin superheavy element sample was prepared and has been continuously counted for spontaneous fission events in a dual surface barrier coincidence counter. In the second experiment, two superheavy element fractions were obtained and were counted for spontaneous fission events; the two fractions contained those elements that co-precipitated with copper sulfide from either an acid or basic solution.