Tripartition in the Spontaneous-Fission decay of Cf252

Abstract

The long-range alpha particles associated with the spontaneous-fission decay of californium-252 have been studied by means of nuclear-emulsion techniques. The alpha energy spectrum was found to peak at about 19 Mev with a half-width of 10 Mev, and the preferential angle of emission was found to be slightly less than 90 deg with respect to the light fission fragment. These results support the view that alpha emission occurs at the time of scission and that the direction is determined by the extent of electrostatic repulsion by the fragments. A trend toward a more nearly symmetric mass division in fission accompanied by alpha emission is indicated. The frequency of occurrence of the long-range alpha particles was observed to be 1 in 415±10% binary fissions. Ternary events consisting of two heavy fragments and one light fragment of short range were observed, but the frequency with which these events occur was not measured. A parallel search was made for ternary-fission events in which fragmentation into comparable masses occurs. © 1961 The American Physical Society.