Enhanced collectivity along the N = Z line: Lifetime measurements in 44Ti, 48Cr, and 52Fe

Abstract Lifetimes of the 2 1 + states in 44 Ti, 48,50 Cr, and 52 Fe were determined with high accuracy exploiting the recoil distance Doppler-shift method. The reduced E2 transition strengths of 44 Ti and 52 Fe differ considerably from previously known values. A systematic increase in collectivity is found for the N = Z nuclei compared to neighboring isotopes. The B ( E2 ) values along the Ti, Cr, and Fe isotopic chains are compared to shell-model calculations employing established interactions for the 0 f 1 p shell, as well as a novel effective shell-model Hamiltonian starting from a realistic nucleon–nucleon potential. The theoretical approaches underestimate the B ( E2 ) values for the lower-mass Ti isotopes. Strong indication is found for particle-hole cross-shell configurations, recently corroborated by similar results for the neighboring isotone 42 Ca.