9 research outputs found
Collective excitations in the transitional nuclei 163Re and 165Re
Excited states in the neutron-deficient nuclei 163
75 Re88 and 165
75 Re90 were populated in the 106Cd(60Ni, p2nγ )
and 92Mo(78Kr, 3p2nγ ) fusion-evaporation reactions at bombarding energies of 270 and 380 MeV, respectively.
γ rays were detected at the target position using the JUROGAM spectrometer while recoiling ions were separated
in-flight by the RITU gas-filled recoil separator and implanted in the GREAT spectrometer. The energy level
schemes for 163Re and 165Re were identified using recoil-decay correlation techniques. At low spin, the yrast
bands of these isotopes consist of signature partner bands based on a single πh11/2 quasiproton configuration.
The bands display large energy splitting consistent with the soft triaxial shape typical of transitional nuclei above
N = 82. The configurations of the excited states are proposed within the framework of the cranked shell model.peerReviewe
First identification of rotational band structures in Re-166(75)91
Excited states in the odd-odd, highly neutron-deficient nucleus 166Re have been investigated via the 92Mo(78Kr,
3p1n)
166Re reaction. Prompt γ rays were detected by the JUROGAM II γ -ray spectrometer, and the recoiling
fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator
and implanted into the Gamma Recoil Electron Alpha Tagging spectrometer located at the RITU focal plane.
The tagging and coincidence techniques were applied to identify the γ -ray transitions in 166Re, revealing two
collective, strongly coupled rotational structures, for the first time. The more strongly populated band structure is
assigned to the πh11/2[514]9/2− ⊗ νi13/2[660]1/2+ Nilsson configuration, while the weaker structure is assigned
to be built on a two-quasiparticle state of mixed πh11/2[514]9/2− ⊗ ν[h9/2f7/2]3/2− character. The configuration
assignments are based on the electromagnetic characteristics and rotational properties, in comparison with
predictions from total Routhian surface and particle-rotor model calculations.peerReviewe
Excited states in the proton-unbound nuclide 158Ta
Excited states in the neutron-deficient odd-odd proton-unbound nuclide 158Ta have been investigated in two
separate experiments. In the first experiment, 166Ir nuclei were produced in the reactions of 380 MeV 78Kr
ions with an isotopically enriched 92Mo target. The α-decay chain of the 9+ state in 166Ir was analyzed. Fine
structure in the α decay of the 9+ state in 162Re established a 66 keV difference in excitation energy between the
lowest-lying 9+ and 10+ states in 158Ta. Higher-lying states in 158Ta were populated in the reactions of 255 MeV 58Ni ions with an isotopically enriched 102Pd target. Gamma-ray decay paths that populate, depopulate, and
bypass a 19− isomeric state have been identified. The general features of the deduced level scheme are discussed
and the prospects for observing proton emission branches from excited states are considered.peerReviewe
Pairing-quadrupole interplay in the neutron-deficient tin nuclei: First lifetime measurements of low-lying states in 106,108Sn
The lifetimes of the low-lying excited states 2+ and 4+ have been directly measured in the neutron-deficient 106,108Sn isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted γ rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the B(E2;21+→0g.s.+) values and it describes well the experimental pattern for 104−114Sn; the B(E2;41+→21+) values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in 108Sn