超微細異常の精密測定による不安定核構造の研究

本研究的目的是通过观察超精细异常，即所谓的Bohr-Weisskopf效应，测量不稳定核磁矩的有限加宽。因此，超精细异常的精确测量提供了远离稳定线的不稳定核结构的重要信息。为此，必须对超精细结构常数和核g因子进行独立的精密测量，我们研制了一台能同时测量超精细结构常数和核g因子的装置：该装置是由三个电磁铁组成的原子束磁共振系统和激光-微波三重共振系统。将来自CERN/ISOLDE质量分离器的不稳定离子束停在中和器中，产生的慢中和原子束通过装置进行三重微波磁共振。原子被光抽运到合适的激发态，然后用微波场去布居，从而使我们能够测量共振态。该装置已成功地用离线稳定Cs束进行了测试，现在已经相当准确地测量了一种不稳定Cs同位素的g因子。我们期待在明年进一步测量各种不稳定Cs同位素的超精细异常。

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 now the g factor of one of the unstable Cs isotopes has been measured with fairly well accuracy. We are expecting to measure hyperfine anomaly of various unstable Cs isotopes further in the next year.