The low-energy $M1\mathrm{}$ component that can be observed in quasicontinuum $\gamma$-ray spectra from heavy-ion reactions is studied within the core-quasiparticle model. Inclusive one-quasiparticle calculations for sequences of isotopes and isotones indicate how the $M1\mathrm{}$ "bumps" vary depending on the structure of the nucleus. Application of the results to higher spins and even-even nuclei is possible on the basis of a spectator quasiparticle hypothesis, which is seen to be adequate qualitatively but not quantitatively.

NUCLEAR STRUCTURE Calculated $M1\mathrm{}$ quasicontinuum $\gamma$-ray spectra, deduced dependences on particle and quasiparticle number. Core-quasiparticle coupling models.

• Received 21 July 1982

DOI:https://doi.org/10.1103/PhysRevC.26.2607