Instituut voor Kern- en Stralingsfysica, K.U. Leuven, University of Leuven, B-3001 Leuven, Belgium.
Phys Rev Lett. 2010 Dec 17;105(25):252502. doi: 10.1103/PhysRevLett.105.252502. Epub 2010 Dec 14.
A very exotic process of β-delayed fission of 180Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post-β-decay daughter nucleus 180Hg (N/Z=1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two 90Zr fragments, with magic N=50 and semimagic Z=40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for β-delayed fission of 180Tl is 3.6(7) × 10(-3)%, approximately 2 orders of magnitude larger than in an earlier study.
通过在 CERN 的 ISOLDE 上使用共振激光电离和随后的质量分离，详细研究了 180Tl 的非常奇特的β延迟裂变过程。与常见的预期相反，后β衰变子核 180Hg（N/Z=1.25）的裂变碎片质量分布是不对称的。这种不对称性更加令人惊讶，因为这个极其缺中子的核的质量对称分裂将导致两个 90Zr 碎片，具有神奇的 N=50 和半魔术 Z=40。这是一种新的不对称裂变，不是由与碎片魔术质子和中子数相关的大壳效应引起的，如在锕系元素区域观察到的那样。新测量的 180Tl 的β延迟裂变分支比为 3.6(7)×10(-3)％，大约比早期研究大两个数量级。
