Studies of the times of emission and multiplicities of K X-rays from fission fragments of specified atomic numbers

Abstract

The average emission times of K x rays emitted from U²³⁶ fission fragments and the multiplicities of K x rays from Cf²⁵² fission fragments of specified atomic numbers have been determined. The average emission times of K x rays from U²³⁶ fragments were determined by detecting the x rays in the two cases of the emitting fragments moving towards and away from the x-ray detector in the time ranges of 110 and 1000 nsec after fission. The most striking delayed K x-ray emitter is found to be ₅₂Te, wherein (79±5)% of the K x rays are emitted in the time interval 110-1000 nsec. Information about the cascade emission of K x rays from Cf²⁵² fission fragments of specified atomic numbers was obtained by measuring the energy spectra of coincident K x rays with two Si(Li) x-ray detectors operated in coincidence with each other and with fission. From the analysis of these spectra the first and second moments of the x-ray emission distribution function were determined. A noteworthy feature of these results is that there exists a significantly large probability for a cascade emission of K x rays in several cases. The cascade emission is found to be, in general, more predominant in the heavy-fragment group as compared to the light-fragment group. In the heavy group, a strong odd-even effect is reflected on the cascade-emission probability. The observed effect on the average K x-ray yield per fragment, if only those events are selected in which the complementary fragment charge has emitted a K x ray, is also discussed.