THE EMISSION OF K-X-RAYS IN SLOW NEUTRON FISSION OF 233U, 235U, AND 239pu*

Present techniques admit the possibility of studying the character of fission fragments with spectroscopic identification of pairs of fragments. The simultaneous measurement of the masses and atomic numbers of fission fragments has been demonstrated in studies of the fission of 252Cf (1). The atomic number is determined by detection of a characteristic x-ray, most often a K-x-ray, emitted by one of the fragments. These x-rays arise from atomic electron vacancies produced by internal conversion in the deexcltation of the fragments (2). Not surprisingly, there is considerable structure in yield as a function of the masses of the fragments (1) and of their atomic numbers (3). The work reported in this letter sought to determine the feasibility of studies of slow neutron induced fission by multiparameter measurements which include K-x-ray identification of atomic number. Such measurements require an appreciable yield of K-x-rays from the fragments, but, more importantly, this method of identification must not introduce an unknown bias in the selection. It is clear that the structure in yields implies that a considerable bias is introduced by requiring the emission of a *Work supported by the Michigan Memorial--Phoenix Project. **Present address: Analytical Division, National Bureau of Standards, Gaithersburg, Maryland.