0000000000367972
AUTHOR
M Scheck
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.
Combined in-beam electron and gamma-ray spectroscopy of 184,186Hg\u2028
By exploiting the SAGE spectrometer a simultaneous measurement of conversion electrons and gamma rays emitted in the de-excitation of excited levels in the neutron-deficient nuclei (184,186)Hg was performed. The light Hg isotopes under investigation were produced using the 4n channels of the fusion-evaporation reactions of (40)Ar and (148,150)Sm. The measured K- and L-conversion electron ratios confirmed the stretched E2 nature of several transitions of the yrast bands in (184,186)Hg. Additional information on the E0 component of the 2(2)(+) -> 2(1)(+) transition in (186)Hg was obtained.
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.
Excited states in Ra-217 populated in the alpha decay of Th-221
The observation of vibrating pear-shapes in radon nuclei (vol 10, 2473, 2019)
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…
α -decay spectroscopy of the N=130 isotones Ra 218 and Th 220: Mitigation of α -particle energy summing with implanted nuclei
An analysis technique has been developed in order to mitigate energy summing due to sequential short-lived α decays from nuclei implanted into a silicon detector. Using this technique, α-decay spectroscopy of the N=130 isotones Ra218 (Z=88) and Th220 (Z=90) has been performed. The energies of the α particles emitted in the Ra218→Rn214 and Th220→Ra216 ground-state-to-ground-state decays have been measured to be 8381(4) keV and 8818(13) keV, respectively. The half-lives of the ground states of Ra218 and Th220 have been measured to be 25.99(10) μs and 10.4(4) μs, respectively. The half-lives of the ground states of the α-decay daughters, Rn214 and Ra216, have been measured to be 259(3) ns and …