Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive $^{222}$Ra and $^{228}$Ra Beams

There is sparse direct experimental evidence that atomic nuclei can exhibit stable pear shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole ($E3$) matrix elements have been determined for transitions in $^{222,228}$Ra nuclei using the method of sub-barrier, multi-step Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of $E$3 matrix elements for different nuclear transitions is explained by describing $^{222}$Ra as pear-shaped with stable octupole deformation, while $^{228}$Ra behaves like an octupole vibrator.

Restoring the valence-shell stabilization in 140Nd

A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain $E2$ and $M1$ transition matrix elements of $^{140}$Nd using the multistep Coulomb-excitation code GOSIA. The absolute $M1$ strengths, $\textrm{B}(M1;2^+_2→2^+_1)=0.033(8)μ^2_N,\textrm{B}(M1;2^+_3→2^+_1)=0.26^{+0.11}_{−0.10}μ^2_N$, and $\textrm{B}(M1;2^+_4→2^+_1)<0.04μ^2_{\textrm{N}}$, identify the $2^+_3$ state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of $^{140}$Nd. The degree of F-spin mixing in $^{140}$Nd was quantified with the determination of the mixing matrix element $V_{\textrm{F−mix}}<7^{+13}_{−7}$keV.

The observation of vibrating pear-shapes in radon nuclei (vol 10, 2473, 2019)

Low-energy Coulomb excitation of Fe-62 and Mn-62 following in-beam decay of Mn-62

Collective 2(1)(+) excitations in Po-206 and Rn-208,Rn-210

In the present study, values have been measured in the 208,210Rn and 206Po nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics at CERN-ISOLDE. These nuclei have been proposed to lie in, or at the boundary of the region where the seniority scheme should persist. However, contributions from collective excitations are likely to be present when moving away from the N=126 closed shell. Such an effect is confirmed by the observed increased collectivity of the transitions. Experimental results have been interpreted with the aid of theoretical studies carried out within the BCS-based QRPA framework. ispartof: European Physical Journal A, Hadrons and Nuclei vo…