全剥离离子 94m Ru 44+ 的衰变研究

在兰州重离子加速器冷却储存环（HIRFL-CSR）上，用等时性质量谱仪首次研究了百微秒量级全剥离离子94mRu44+的衰变。94mRu44+由初级束流112Sn轰击Be靶产生，经过放射性束流线RIBLL2的筛选后注入到等时性设置的实验环CSRe中，并利用安装在实验环中的飞行时间探测器测量离子在CSRe中的循环周期。94mRu44+退激引起的质量改变会带来其循环周期的变化，由此直接观测到了94mRu44+退激到基态的过程。确定了本次实验中衰变事例探测的灵敏区间，并讨论了衰变发生时刻的测量精度。同时，测量了短寿命核素94mRu44+的质量，其半衰期约为100 μs，这是目前储存环质量谱仪测量的最短寿命核素的质量。 The decay of the fully stripped ion 94mRu44+ in the order of one hundred microseconds has been studied for the first time by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou. 94mRu44+ was produced via projectile fragmentation of a 112Sn primary beam bombarding on a 9Be production target. After the in-flight separation with RIBLL2, the ions were injected into the experimental ring (CSRe) and then stored there. The revolution times of the stored ions were measured by a Time-of-Flight (TOF) detector. Due to the mass change of a 94mRu44+ ion caused by its de-excitation to the ground state, hence the revolution time change, the decay process of 94mRu44+ could be directly observed in the CSRe. The sensitive window for detection of the decay events and the measurement precision of the decay time have been determined in this work. At the same time, we measured the mass of short-lived 94mRu44+ with the half-life about one hundred microseconds, which is the shortest among nuclides that have been studied by using storage-ring mass-spectrometry.