Study on the Decay of the Fully Stripped Ion ^94mRu⁴⁴⁺

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.