Muonic x-ray measurement of the monopole and quadrupole charge parameters ofGd154−158,160

Publisher Website
Google Scholar
Abstract
Monopole and quadrupole charge distributions of Gd154, Gd155, Gd156, Gd157, Gd158, and Gd160 were investigated by muonic-atom K and L x-ray measurements. The model-independent Barrett charge radii Rk and the isotope shifts ΔRk were measured, and values of 〈r2〉 and Δ〈r2〉 were deduced. A pronounced even-odd staggering effect of the nuclear charge radii was observed for the series Gd156−158. The quadrupole moments of the first excited states of the even-A Gd nuclei were determined to be Q154(2+)=−1.82(4) e b, Q156(2+)=−1.93(4) e b, Q158(2+)=−2.01(4) e b, and Q160(2+)=−2.08(4) e b, and the quadrupole moments of the 32− ground states of the odd-A Gd155,157 nuclei were determined to be Q155(32−)=1.27(3) e b and Q157(32−)=1.35(3) e b. Comparison with a separate measurement of the odd-A ground-state quadrupole moments based on the static hyperfine splitting of the muonic M x rays showed that the model error in the extracted quadrupole moments of these nuclei is less than 2 percent. The quadrupole moments and the B(E2) values obtained in the present experiment for the low-lying Gd states are in satisfactory agreement with the axially symmetric rotational model. However, the Gd154 nucleus exhibits a considerable softness as indicated by the isomer shift of the 2+ excited state and by the experimental value of the ratio Q(2+)B(E2:0+→2+).