P. Sarriguren et al., SPIN-DEPENDENT AND DEFORMATION-DEPENDENT ORBITAL M1 STRENGTH IN RARE-EARTH NUCLEI, Journal of physics. G, Nuclear and particle physics, 20(2), 1994, pp. 315-337
The M1 excitations in three isotope chains, Nd-142, Nd-146, Nd-148, Nd
-150, Sm-144, Sm-148, Sm-150, Sm-152, Sm-154, and Gd-156, Gd-158, are
studied within the quasi-particle random-phase approximation using a m
ean field given by a deformed Woods-Saxon potential and including quad
rupole-quadrupole and spin-spin residual inter-actions. A residual rot
ation-vibration coupling ensures the exclusion of the spurious state.
The behaviour of the M1 strength distribution is studied systematicall
y in the whole range of experimentally explored excitation energies an
d compared with the large variety of experimental information, which i
ncludes both low-lying orbital and higher-lying spin-flip 1+ excitatio
ns. We have found a quadratic dependence of the Ml strength summed up
to 4 MeV on the nuclear deformation reproducing at the same time the m
ain features of the low-lying Ml spectra. The double-peaked structure
of the spin M1 strength distribution found experimentally in several n
uclei is qualitatively reproduced and interpreted as isoscalar and iso
vector peaks.