通过44Cr的精确质量测量研究其衰变

Accurate mass data of 44Cr can be used to test isobaric multiplet mass equation (IMME) for T=2, Jπ=0+, A=44 quintet and predict the masses of the isobaric analog states (IASs). The assignment of T=2 IAS in 44V has been questioned. Combining investigations of the research results about 44Cr decay with shell-model calculations, we reconstructed the partial decay scheme of 44Cr and proposed new IAS assignment in 44V. It is found that the strongest proton peak in the decay of 44Cr is from the deexcitation of the 1+ excited state in 44V, not from the 0+, T=2 IAS state, which is different from the conventional identification of IASs from the β-delayed proton emissions. Due to the difficulties of β-γ measurement of 44Cr, we plan to precisely measure the mass of 44Cr using Isochronous Mass Spectrometry (IMS) in the storage ring CSRe instead, precision better than 50keV is expected to be achieved. The mass of IAS for 44V can be deduced by IMME and it can be compared with the assigned value in order to confirm the new assignment. This finding has important implications on the identification of the IASs from β-delayed charged-particle emission studies.

精确的44Cr质量数据可以用来检验同位旋多重态质量方程（IMME）在A=44，T=2，Jπ=0+五重态中的适用性，预言同位旋相似态（IAS）的质量。44V中T=2的IAS态指认一直存在争议。通过分析、总结44Cr衰变相关的研究成果，结合理论壳模型计算，我们重新构建了44Cr的部分衰变纲图并且建议了44V新的IAS态，发现：衰变分支比最大的β缓发质子来自44V中1+激发态的退激发，而不是通常认为的0+、T=2的IAS态。为了验证新指认的IAS态，在IAS态的γ跃迁存在产额低、本底高、难测量的情况下，另辟蹊径，计划在CSRe储存环等时性质量谱仪上测量44Cr的质量，要求精度好于50keV，利用IMME公式精确预言44V的IAS态质量，通过比对预言值确认IAS态的指认。该研究对β缓发带电粒子放射性研究中IAS态的鉴别有重要意义。

V-44中T=2的IAS态指认一直存在争议，计划通过测量Cr-44的质量，利用局域质量公式（同位旋多重态质量方程），精确预言V-44的IAS态质量，指认IAS态。实验在CSRe储存环等时性质量谱仪上进行，使用Ni-58束流轰击铍靶，发生弹核碎裂反应产生目标核素Cr-44。经过对飞行时间谱的分析，首次确定Cr-44的质量为-13422(51) keV，质量分辨能力达到一百万。据此给出V-44中IAS态的质量和Cr-44可能的部分衰变纲图。该建议的纲图可为衰变实验提供指导，预言衰变信息。