Magnetic Moments of Proton Drip-Line Nuclei and Abnormal Breaking of Isospin Symmetry

我们已经确定了^9C、^<113>Q、^<19>Q和21F的核磁矩。结果表明，^9C-^<13>对中出现的磁矩异常行为，即异常的自旋期望值或异常的g因子相关性，在^<13> -^<13 b> B的镜像对中没有出现。对于^<19> 0和^<21>F的情况，由于^<19>Q的伴子不存在，而且^<21>F的伴子^<21>Mg的磁矩还不知道，因此无法进行镜像对分析的讨论。然而，与每个原子核的理论计算进行比较是可能的。使用shell模型代码OXBASH (int。psdMK， PW)在^<13>Q, ^<19>Q和^<21>F的实验值都与实验值在几个%内一致。这一事实使得^9C-^9Li对的不规则性更加突出。因此，这就暗示了^9C-^9Li对的异常不是同位旋T = 3/2镜像对的共同特征，而是由于^9C-^9Li对的特殊情况。目前还没有一个成功的理论能很好地再现^9C-^9Li对的异常。^9C-^9Li仍然有三种可能，如下所示。i)同位旋对称断裂；ii)偶核群配对断裂；iii)核子的有效g因子在很大程度上重整化。如果我们使用双闭壳层实验确定的有效g因子，我们发现^9C-^9Li的自旋期望值接近理论计算值。这一事实使上述问题引起人们的注意。最近关于A=9系统核结构的AMD或集群模型的理论工作正在密集发展，可能在不久的将来为解决这一问题提供关键。

We have determined the nuclear magnetic moments of ^9C, ^<113>Q, ^<19>Q, and 21F.As a result, the abnormal behavier of magnetic moments seen in ^9C-^<13>0 pair, i.e. the abnormal spin expectation value or the unusual g-factor correlation, was not seen in the mirror pair of ^<13>0-^<13>B, For the cases of ^<19>O and ^<21>F, discussions using mirror-pair analyses can not be made because the partner of ^<19>Q is absent and the magnetic moment of ^<21>Mg, the partner of ^<21>F, has not been known yet. However, comparisons with theoretical calculations for each nucleus are possible. The results of calculations with the shellmodel code OXBASH (int. psdMK, PW) are all in good agreement with the experimental values within a few % for ^<13>Q, ^<19>Q, and ^<21>F.This fact has made the irregularity of ^9C-^9Li pair stand out. Therefore that is an implication that the abnormality of ^9C-^9Li pair is not a common feature of isospin T = 3/2 mirror pairs and it is due to the special situation for ^9C-^9Li pair. There has not been a successful theory yet that well reproduces the abnormality of ^9C-^9Li pair. There are still three possiblities for ^9C-^9Li pair as follows. i) Isospin symmetry breaks, ii) pairing of the even-number nucleon group breaks largely, iii) effective g-factors of nucleons are largely renormalized. If we use the effective g-factors determined experimentally at the double closed shell, the spin expectation value for ^9C-^9Li is found to get a value near the theoretical calculation. This fact makes the above iii) attract an attention. Recent theoretical works with AMD or cluster models on the nuclear structure of the A=9 system developping intensively might give a key to this problem in the near future.