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  • Author: Y. Ichikawa x
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Short-lived nuclides of iodine produced in the proton-, 12C- and 19F-induced fission of 235U, 237Np and 238U were separated with a rapid chemical separation system SISAK. Relative yields of the nuclides were determined by γ -ray spectrometry to obtain the isomeric yield ratios of 134mI/134gI and 136mI/136gI. Angular momenta of the fission fragments, 134I and 136I, were derived from the measured isomeric yield ratios by the spin-dependent statistical model. In the light- and heavy-ion fission, variation of the observed angular momenta can be explained by the excitation energies of the fissioning nuclei and the spherical shell structure with N = 82.

Hydrogen-doped alkali-metal fullerides were studied by means of mass-analyzed thermal desorption and positron annihilation. The hydrogen desorption spectra reveal the inclusion of hydrogen in the fullerides as two types of components; one weakly adsorbed and the other strongly bound, probably as hydride ion. The positron lifetime spectra demonstrate that hydrogen-doping to alkali-metal fullerides increases a concentration of higher-order vacancy-type defects, through which more than 50% injected positrons decay with a lifetime of 0.42–0.71 ns.

The transactinide nuclides 261Rf and 262Db have been successfully produced in the 248Cm(18O,5n) reaction at 99 MeV and in the 248Cm(19F,5n) reaction at 100, 103, and 106 MeV, respectively, at the JAERI tandem accelerator. The on-line ion exchange experiments with an automated fast and repetitive liquid chromatography separation system were performed in the HNO3/HF system using Rf homologues 89mZr and 167,165Hf produced in the 89Y(p,n) and 152Gd(18O,xn) reactions, respectively. The radiotracers 88Zr, 175Hf, and 234Th were also prepared and the distribution coefficients on ion exchange resins were measured systematically in 1-11 M HCl and 1-14 M HNO3 with the batch method. It was found that anion exchange experiments of Rf in 8 M HNO3 and 9 M HCl provided information useful to extract the ionic radius of Rf and to verify the influence of relativistic effects.