Study of unstable nuclear structure through hyperfine anomaly

本研究的目的是通过观察超精细异常，即所谓的玻尔-魏斯科普夫效应，来测量不稳定原子核磁矩的有限展宽。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，超精细结构常数和核g因子的精确测量必须独立进行。我们建立了一个可以独立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。来自CERN/ISOLDE质量分离器的不稳定离子束在中和器中停止，然后产生缓慢中和的原子束通过装置进行三重微波磁共振。原子被光泵浦到一个合适的激发态，然后用应用的微波场去填充，从而使我们能够测量共振。该装置成功地进行了离线稳定铯束测试，并提取了稳定K和Rb核超精细异常的精确数据。该仪器现在安装在欧洲核子研究中心的ISOLDE实验大厅，并准备用于不稳定核的在线超精细异常测量。我们期待今年首次对超精细异常进行在线测量。

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.