The isotope shifts of the radii of the distributions of neutron and nucleon matter in the samarium isotopes are deduced by combining data from x-ray, muonic x-ray, and optical isotope shift measurements of charge (proton matter) radii with data for the isotope shifts of Coulomb displacement energies. The average isotope shifts from $A=144\mathrm{}$ (spherical) to $A=154\mathrm{}$ (deformed) are nearly the same for proton and neutron matter with ${\gamma }_N\approx 1.3$ or ${〈r^2〉}^{\frac{1}{2}}\propto A^{0.43}$. The neutron matter radii increase more rapidly than the proton matter radii in the region of the light transitional Sm isotopes. The transition from spherical to deformed ground states between $N=88\mathrm{} \mathrm{and} 90$ is accompanied by a strong increase in the radius of the proton matter distribution (${\gamma }_N\approx 1.9$), whereas the radius of the neutron-excess matter distribution remains almost constant (${\gamma }_N\approx 0.0$). The data suggest strong even/odd staggering effects for both proton and neutron matter radii which are out of phase. The droplet model of the atomic nucleus when combined with experimental deformation parameters describes the isotope shift of the charge radii very well. The influence of zero-point vibrations in the light transitional Sm isotopes is apparent. The isotope shift of the neutron matter radii appears to be overestimated. The interacting boson model is found to describe the isotope shift of neutron matter radii satisfactorily but fails to reproduce the isotope shift of the charge radii.

NUCLEAR STRUCTURE Deduced isotope shifts of neutron-excess, neutron, and nucleon matter radii. Interpretation of isotope shifts of proton and neutron matter radii with droplet model and interacting boson model.

• Received 28 December 1982

DOI:https://doi.org/10.1103/PhysRevC.27.2282