Enhanced Quadrupole and Octupole Strength in Doubly Magic ^{132}Sn.

International audience; The first $2^+$ and $3^-$ states of the doubly magic nucleus $^{132}$Sn are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The $^{132}$Sn ions are accelerated to an energy of 5.49  MeV/nucleon and impinged on a $^{206}$Pb target. Deexciting $\gamma$ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions $0_{g.s.}^+ \rightarrow 2_1^+$, $0_{g.s.}^+ \rightarrow 3_1^-$, and $2_1^+ \rightarrow 3_1^-$ in $^{132}$Sn. The res…

Structure of low-lying states in 140Sm studied by Coulomb excitation

The electromagnetic structure of 140Sm was studied in a low-energy Coulomb excitation experiment with a radioactive ion beam from the REX-ISOLDE facility at CERN. The 2+ and 4+ states of the ground-state band and a second 2+ state were populated by multistep excitation. The analysis of the differential Coulomb excitation cross sections yielded reduced transition probabilities between all observed states and the spectroscopic quadrupole moment for the 2+ 1 state. The experimental results are compared to large-scale shell model calculations and beyond-mean-field calculations based on the Gogny D1S interaction with a five-dimensional collective Hamiltonian formalism. Simpler geometric and alge…

New ß-decaying state in 214Bi

New β-decaying state in 214Bi

A new β-decaying state in 214Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred Iπ = (8−) assignment was suggested for this state based on the β-decay feeding pattern to levels in 214Po and shell-model calculations. The half-life of the Iπ = (8−) state was deduced to be T1/2 = 9.39(10) min. The deexcitation of the levels populated in 214Po by the β decay of this state was investigated via γ -γ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in 214Bi and 214Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both ca…

Search for the terminating 27- state in 140Nd

In the search for the fully aligned 27− state in 140Nd predicted by cranked Nilsson-Strutinsky calculations, new close-to-spherical high-spin states have been discovered. Both the close-to-spherical and the triaxial calculated states are in good agreement with the experimental results, supporting the existence of shape coexistence up to very high spins. Shell-model calculations using a newly developed effective interaction for the 50 N ,Z 82 mass region are in good agreement with the observed spherical states. The comparison between the experimental and calculated level energies allowed the relative energy to be established between several proton and neutron orbitals at high energy and spin…

Nuclear structure of Te isotopes beyond neutron magic number N=82

15 pags., 10 figs., 4 tabs.

Yrast 6+Seniority Isomers of136,138Sn

Delayed γ-ray cascades, originating from the decay of (6⁺) isomeric states, in the very neutron-rich, semimagic isotopes (136,138)Sn have been observed following the projectile fission of a ²³⁸U beam at RIBF, RIKEN. The wave functions of these isomeric states are proposed to be predominantly a fully aligned pair of f(7/2) neutrons. Shell-model calculations, performed using a realistic effective interaction, reproduce well the energies of the excited states of these nuclei and the measured transition rates, with the exception of the B(E2;6⁺→4⁺) rate of ¹³⁶Sn, which deviates from a simple seniority scheme. Empirically reducing the νf(7/2)(2) orbit matrix elements produces a 4₁⁺ state with alm…

The structure of low-lying states in ${}^{140}$Sm studied by Coulomb excitation

The electromagnetic structure of $^{140}$Sm was studied in a low-energy Coulomb excitation experiment with a radioactive ion beam from the REX-ISOLDE facility at CERN. The $2^+$ and $4^+$ states of the ground-state band and a second $2^+$ state were populated by multi-step excitation. The analysis of the differential Coulomb excitation cross sections yielded reduced transition probabilities between all observed states and the spectroscopic quadrupole moment for the $2_1^+$ state. The experimental results are compared to large-scale shell model calculations and beyond-mean-field calculations based on the Gogny D1S interaction with a five-dimensional collective Hamiltonian formalism. Simpler …

Search for the terminating27−state inNd140

In the search for the fully aligned 27(-) state in Nd-140 predicted by cranked Nilsson-Strutinsky calculations, new close-to-spherical high-spin states have been discovered. Both the close-to-spherical and the triaxial calculated states are in good agreement with the experimental results, supporting the existence of shape coexistence up to very high spins. Shell-model calculations using a newly developed effective interaction for the 50 <= N, Z <= 82 mass region are in good agreement with the observed spherical states. The comparison between the experimental and calculated level energies allowed the relative energy to be established between several proton and neutron orbitals at high energy…

Enhanced Quadrupole and Octupole Strength in Doubly Magic Sn132

The first 2+ and 3- states of the doubly magic nucleus Sn132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb206 target. Deexciting γ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0g.s.+→21+, 0g.s.+→31-, and 21+→31- in Sn132. The results on these states provide crucial information on cross-shell configurations which are determined within large-sca…

Proton-Neutron Pairing Correlations in the Self-Conjugate NucleusK38Probed via a Direct Measurement of the Isomer Shift

A marked difference in the nuclear charge radius was observed between the ${I}^{\ensuremath{\pi}}={3}^{+}$ ground state and the ${I}^{\ensuremath{\pi}}={0}^{+}$ isomer of $^{38}\mathrm{K}$ and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of $⟨{r}_{\mathrm{c}}^{2}⟩{(}^{38}{\mathrm{K}}^{m})\ensuremath{-}⟨{r}_{\mathrm{c}}^{2}⟩{(}^{38}{\mathrm{K}}^{g})=0.100(6)\text{ }\text{ }{\mathrm{fm}}^{2}$ was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement fr…

Evolution of proton single-particle states in neutron-rich Sb isotopes beyond N=82

11 pags., 8 figs., 2 tabs.