Magnetic dipole response in nuclei at the N=28 shell closure: a new look

The magnetic dipole response of N = 28 isotones is obtained for Ca-48, Ti-5 0, Cr-52 and Fe-54 by means of shell model calculations in the full pf-shel l. Spin quenching factors derived in all four nuclei by comparison to exper imental strengths from electron scattering agree well with each other. The deduced effective g-factor g(s)(eff) = 0.75(2) g(s)(free) is consistent wit h findings for the Gamow-Teller strength in this mass region. The ability o f state-of-the-art shell-model calculations to describe the gross propertie s and the fragmentation of the complex experimental B(M1) strength distribu tions is investigated. (C) 1998 Elsevier Science B.V. All rights reserved.