A possible excitation scheme of particle-hole states in $N\ne Z$ nuclei is worked out within the isospin formalism. Particle-hole states with a definite isospin are decomposed into 1p-1h (particle-hole), 2p-2h, and 3p-3h states. This decomposition enables us to relate transition strengths from the ground state to the excited states and those in the adjacent nuclei. The same thing is done for $\Delta$ isobar-hole states. Using these results, we obtain the relations among the quenching strengths of magnetic transitions in $N\ne Z$ nuclei. In particular, we apply these relations to the $M1\mathrm{}$ states around ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and compare the results with experimental data obtained by ($p, n$), ($p, p^{\prime }$), and ($e, e^{\prime }$) experiments on ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$.

NUCLEAR STRUCTURE Isospins, $\Delta$ isobar polarization.

• Received 22 February 1982

DOI:https://doi.org/10.1103/PhysRevC.26.1256