Spectroscopy of 2565,67Mn: Strong coupling in the N = 40 “island of inversion”

Abstract Excited states in 63,65,67 Mn were studied via in-beam γ -ray spectroscopy following knockout reactions from 68 Fe. Similar level schemes, consisting of the 11/2 − , 9/2 − , 7/2 − and 5/2 g . s . − level sequence, connected by I → I − 1 transitions, were established, the first time for 65,67 Mn. Their level structures show features consistent with strongly-coupled rotational bands with K = 5 / 2 . State-of-the-art shell-model calculations with the modified LNPS effective interaction reproduce the observed levels remarkably well and suggest the dominance of 4-particle-4-hole neutron configurations for all the states. The data on the low-lying excited states of odd-mass 53−67 Mn provide a textbook example of nuclear structure evolution from weak coupling through decoupling to strong coupling along a single isotopic chain on the n-rich side of the β stability line. These results help to deepen our understanding of the N = 40 “island of inversion”.