Times of Emission ofKX Rays fromCf252Fission Fragments of Known Mass

The measured yield of $K$ x rays emitted from fission fragments of ${\mathrm{Cf}}^{252}$ is reported as a function of the time after fission for times between 1 and 56 nsec, and as a function of the mass of the fragment emitting the X ray. In the experiment, three-parameter data were recorded event by event. The first and second parameters contained information about the energies of both fission fragments from which it was possible to calculate the mass of each fragment. The third parameter contained a signal that was proportional to the time that elapsed between the detection of one of the fission fragments and the detection of an X ray. The timing data were sorted to yield X-ray timing spectra for fission-fragment mass intervals 4 amu wide. Each timing spectrum was fitted with a function that was derived from folding the prompt-response function of the system into a sum of three exponential decays. This analytical technique permitted the determination of the percent of the total X-ray emissions coming from each of the three half-life groups. These results, in conjunction with the yield data, were then interpreted in terms of fragment excitation states and comparisons were made with previously reported data.