The ionic charge distribution of fission products and the influence of internal conversion on highly preionized heavy ions

At the mass spectrometer LOHENGRIN of the Institut Laue-Langevin the ionic charge state distributions of²³⁵U(n _th,f)-fission products separated according to their mass, nuclear charge and kinetic energy were determined. The mean values and the widths of the ionic charge state distributions are compared with semiempirical predictions. Deviations between the experimental data and the estimation of Nicolaev and Dmitriev are found. Furthermore, the influence of the internal conversion process on the ionic charge state distribution of highly ionized fission products was established. Internal conversion is observed mainly for odd-odd nuclei and nuclei with 59 neutrons. The Auger cascade following the internal conversion process shifts the ionic charge state distribution by about 3 charge units. The yield of conversion electrons per fragment was determined in the mass range 85≦A≦103.