K X-ray yields in 0-1 μs from ²³⁶U fragments

Abstract

The yields of K X-rays emitted in the time range 0-1μs by fragments of specified nuclear charges have been determined in the thermal fission of ²³⁵U with a high-resolution (0.9 keV FWHM at 26.25 keV) Si(Li) spectrometer. The fission fragments were detected in nearly 2π geometry by a silicon semiconductor detector placed at a distance of 0.5 mm from the source foil to ensure that the X-rays were emitted close to the source foil after the fragments have come to rest. The spectra of K X-rays in coincidence with fission were analysed by a least-square fitting code to determine the total number of K X-rays emitted per fission from fragments of different atomic numbers. Using the known fragment charge yield, the above results were transformed to obtain the K X-ray yield per fragment as a function of fragment charge. The present results are compared with those in the time interval 0-1 ns to obtain information on the X-ray half-lives for fragment nuclei of different atomic numbers.