Spectroscopy of the T=3/2 A=47 and A=45 mirror nuclei via one- and two nucleon knockout reactions

The charge-dependent interaction between nucleons can be explored and exploited using the analogue states identified in mirror nuclei. A cascade of excited states was established for the first time in the Tz = −3/2 proton-rich nuclei, 47Mn (Z = 25, N = 22) and 45Cr (Z = 24, N = 21), using an in-beam gamma-ray spectroscopy experiment. The observed states in the proton-rich nuclei were compared to their well-studied Tz = +3/2 mirror nuclei, 47Ti (Z = 22, N = 25) and 45Sc (Z = 21, N = 24), respectively. Analogue one- and two-nucleon knockout reactions were exploited using the 48Mn/48V and 47Cr/47V incoming secondary beams to populate states in 47Mn/47Ti and 45Cr/45Sc, respectively. New level schemes of the proton rich 47Mn and 45Cr nuclei were established using mirror symmetry arguments and gamma-gamma coincidence analysis. The inclusive and exclusive knockout cross sections in the A = 47 mirror pair have been measured for the observed populated states and were compared to reaction model calculations. Large differences between the cross sections of both mirror reactions were found to result from the large binding-energy differences between both nuclei. Large-scale shell-model calculations and an in-development density-functional approach, using the no-core configuration-interaction (DFT-NCCI) method, were deployed to study the mirror energy differences (MED) between the isobaric T = 3/2 states for the 47Mn/47Ti and 45Cr/45Sc mirror pairs. The inclusion of the isospin-breaking terms provides a stringent test of the model prescriptions due to the active presence of the fp- and sd-orbitals and, for the case of 45Cr, the spherical and deformed states that co-exist near the ground state. Lastly, the mean lifetimes of the first excited 7/2− yrast states in the A = 47 nuclei were measured using the gamma-ray lineshape method. The mean lifetime of the yrast 7/2− states in 47Ti and 47Mn were found to be t=331(15) ps and t=687(36) ps, respectively. As these two mirror transitions are almost-pure M1 transitions, a high-precision comparison of the mirrored B(M1) strengths were performed, resulting in identical transition strengths to a precision of 10%.