缺中子核素 101 In低位同核异能态的首次观测

在兰州重离子加速器冷却储存环（HIRFL-CSR）上，用初级束流112Sn35+轰击了靶厚约10 mm的Be靶，产生了101In的基态和低位同核异能态。这些实验产生的碎片每25 s经过放射性束流线RIBLL2的筛选后注入到实验环CSRe中，利用飞行时间探测器测量离子在CSRe中的回旋周期。在此次实验中，磁场晃动会导致离子在环内的循环周期发生改变，传统的离子鉴别方法难以完成大部分离子的鉴别。通过发展和运用单次注入离子鉴别这一新的离子鉴别方法，有效地消除了磁场晃动对于离子鉴别的影响，并清楚地将101In基态和低位同核异能态鉴别出来，从而首次在实验中观测到101In的低位同核异能态。实验得到的激发能与理论外推值在112 keV的误差范围内一致，其低位同核异能态的寿命大于200 μs。 Isochronous mass spectrometry has been applied to 112Sn projectile fragments at the HIRFL-CSR facility in Lanzhou. To produce short-lived nuclei of interest, we used projectile fragmentation of 112Sn35+ primary beams in a~10 mm thick 9Be production target. The fragments were selected and analyzed by RIBLL2 and injected into the experimental storage ring(CSRe) every 25 s. To measure revolution times of stored ions,we used a Time-Of-Flight detector installed in CSRe. A new particle identification method was developed to distinguish ions on the measured revolution time spectrum for each injection. Based on this method, the shifts of the revolution time due to instable dipole magnet fields can be corrected and the ground and isomeric states of 101In have been well-resolved. The measured excitation energy is consistent with the theoretical value in the error range of 112 keV. The lifetime of the isomeric states of 101In is more than 200 μs.