同位旋是核物理中用于描述核力的电荷无关性的一个基本概念，其对称性破缺研究有助于人们深入认识核力和复杂的原子核结构，具有十分重要的意义。目前同位旋对称性破缺研究主要集中在sd壳层，在更重质量的fp壳层核区，相关的实验数据较少且精度不高，亟需进行更多高精度的实验研究。本项目计划在兰州重离子加速器RIBLL1次级束流线上对45Cr、49Fe等fp壳核区的丰质子核素的beta+衰变进行测量。研究其子核45V和49Mn的同位旋相似态的gamma和质子衰变。一方面通过测量到的衰变能计算出同位旋相似态的质量，对同位旋多重态质量公式进行精确检验，另一方面将测量到的gamma和质子分支比和壳模型理论计算进行比较，得到同位旋相似态的同位旋不纯度。对fp壳核区的同位旋对称性破缺进行系统性研究。

Isospin is a fundamental concept for describing the charge-independence of the nuclear force in nuclear physics. The study of the isospin symmetry breaking is very important because it can help us to deeply understand nuclear force and nuclear structure. The current investigation of the isospin symmetry breaking mostly focuses on the sd-shell nuclei, whereas there are few experimental data with low precision in the fp-shell region, thus more precise measurements are highly desirable. The present proposal plans to measure beta+ decay of the proton-rich nuclei in fp-shell region, e.g. 45Cr and 49Fe, at the HIRFL-RIBLL1 facility, and investigate the the gamma and proton decay of the isobaric analog states in 45V and 49Mn. The gamma and proton decay energies will be used to deduce the masses of the isobaric analog states and the isobaric multiplet mass equation will be verified. The branching ratios of the gamma and proton decay will be used to extract the isospin impurities of the isobaric analog states. The above studies will help us better understand the isospin symmetry breaking in the fp-shell nuclear region.