The dependence on the properties of the effective interaction of the energies of and excitation strengths to magnetic dipole states in open shell nuclei is studied. In particular the single j-shell for 48Ti is used as an example. In this case there are two 1+ states with isospin T = 2 and one with isospin T = 3. The conditions for having a strong low-lying collective 1+ state are examined. Focus is also given on the excitation strength to the analog T = 3 state since this is of relevance also to β+ Gamow-Teller reactions and to double beta decay. It is found that in the rotational limit there is no strength to the T = 3 state and there is an overly strong low-lying 1+T = 2 state. This is almost also true for a quadrupole-quadrupole interaction. At the other extreme, as shown by Halse, with a pairing interaction all the strength goes to the T = 3 state. Other interactions considered are pairing plus quadrupole, spin-dependent delta and Kuo-Brown bare and renormalized, and matrix elements taken from the spectrum of 42Sc. It is found that the β+ strength can be reduced either by making the two-body J = 2 T = 1 matrix element or J = 1 T = 0 matrix element more attractive, just as was shown by others in heavier nuclei. However such parameter changes have effects on other properties of the 1+ spectrum, which can serve as indicators as to whether or not these changes are justified.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics