Internal-Conversion Electrons Emitted by Different Elements in the Fission ofCf252

Abstract

Coincidence measurements of the internal-conversion electrons and x rays emitted by the fragments and products of the spontaneous fission of ${\mathrm{Cf}}^{252}$ are reported. In the experiment, two-parameter data were recorded event by event and stored sequentially on magnetic tape. The first parameter contained information on the energy of the x ray as measured by a high-resolution semiconductor detector and was used to determine the atomic number of the de-exciting nucleus. The second parameter contined information on the energy of the internal-conversion electrons. Two measurements were performed. The first measurement recorded only electrons emitted from the pre-$\ensuremath{\beta}$-decay fission fragments, while the second measured events from both the fragments and products of fission. In general it was found that the x rays from an element are produced by numerous internal-conversion transitions. The energies of these transitions are tabulated for each element produced in fission. A greater number of these transitions were observed to occur for odd-$Z$ elements than for even-$Z$ elements suggesting the even-even nuclides contribute little to the x-ray spectrum. This even-odd effect was more pronounced in the measurement of events from both fragments and products of fission than in the measurement of events from the fission fragments alone.