Study of unstable nuclear structure through hyperfine anomaly

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The aim of the present investigation is to measure the finite broadening of magnetic moment of unstable nuclei through the observation of the hyperfine anomaly, so called Bohr-Weisskopf effect. Precision measurements of the hyperfine anomaly thus provide important information on the structure of unstable nuclei far from the stability line. For this purpose, precision measurements of both the hyperfine structure constant and nuclear g-factor have to be performed independently.We have constructed an apparatus with which we can measure both the hyperfine structure constant and the nuclear g-factor independently : The apparatus is of atomic-beam magnetic resonance system consisting mainly of three electromagnets and laser-microwave triple resonance system. Unstable ion beam from the CERN/ISOLDE mass separator is stopped in a neutralizer and then produced slow neutralized-atomic-beam is passed through the apparatus to perform the triple microwave magnetic resonance. The atoms are optically pumped to a suitable excited states and then depopulated with the applied microwave fields, thus enabling us to measure the resonances.The apparatus was successfully tested with off-line stable Cs beam and the precise data on the hyperfine anomaly of stable K and Rb nuclei have been extracted. The apparatus is now set-up at the CERN ISOLDE experimental hall, and is ready to be used for the on-line hyperfine anomaly measurements of unstable nuclei. We are expecting the first on-line measurements of hyperfine anomaly this year.