High-spin states beyond the proton drip-line: Quasiparticle alignments in 113Cs (original) (raw)
Related papers
Rotational structures in the 125Cs nucleus
The European Physical Journal A, 2006
The collective band structures of the 125 Cs nucleus have been investigated by in-beam γ-ray spectroscopic techniques following the 110 Pd (19 F, 4n) reaction at 75 MeV. The previously known level scheme, with rotational bands built on πg 7/2 , πg 9/2 and πh 11/2 orbitals, has been extended and evolves into bands involving rotationally aligned ν(h 11/2) 2 and π(h 11/2) 2 quasiparticles. A strongly coupled band has been reassigned a high-K πh 11/2 ⊗νg 7/2 ⊗νh 11/2 three-quasiparticle configuration and a new side band likely to be its chiral partner has been identified. Configurations assigned to various bands are discussed in the framework of Principal/Tilted Axis Cranking (PAC/TAC) model calculations. PACS. 21.10.Re Collective levels-23.20.Lv γ transitions and level energies-21.60.-n Nuclear-strucutre models and methods-27.60.+j 90 ≤ A ≤ 149
Rotational structures in 123 Cs
European Physical Journal A, 2005
High-spin states in 123Cs, populated via the 100Mo ( 28Si, p4n) fusion-evaporation reaction at E lab = 130 MeV, have been investigated employing in-beam γ-ray spectroscopic techniques. Rotational bands, built on πg 7/2, πg 9/2 and the unique-parity πh 11/2 orbitals, have been extended and evolve into bands involving rotationally aligned ν(h 11/2)2 and π(h 11/2)2 quasiparticles. A three-quasiparticle band based on the high-K πh 11/2 ⊗ νg 7/2 ⊗ νh 11/2 configuration has also been observed. Total Routhian Surface (TRS) calculations have been used to predict the nuclear shape parameters ( β2, β4, γ) for the various assigned configurations. The assigned configurations have been discussed in the framework of a microscopic theory based on the deformed Hartree-Fock (HF) and angular-momentum projection techniques.
Triaxiality and exotic rotations at high spins in 134 Ce
High-spin states in 134 Ce have been investigated using the 116 Cd(22 Ne ,4n) reaction and the Gammasphere array. The level scheme has been extended to an excitation energy of ∼30 MeV and spin ∼54. Two new dipole bands and four new sequences of quadrupole transitions were identified. Several new transitions have been added to a number of known bands. One of the strongly populated dipole bands was revised and placed differently in the level scheme, resolving a discrepancy between experiment and model calculations reported previously. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. A coherent understanding of the various excitations, both at low and high spins, is thus obtained, supporting an interpretation in terms of coexistence of stable triaxial, highly deformed, and superdeformed shapes up to very high spins. Rotations around different axes of the triaxial nucleus, and sudden changes of the rotation axis in specific configurations, are identified, further elucidating the nature of high-spin collective excitations in the A = 130 mass region.
Maximally aligned states in the proton drip line nucleus Sb-106
Nuclear Physics A, 2005
High-spin states in 106 Sb have been investigated in the 54 Fe(58 Ni, 1α1p1n) reaction by in-beam γ-spectroscopic methods using the EUROBALL detector array equipped with charged particle and neutron detectors. On the basis of measured γ γ-coincidence relations, angular distributions, and linear polarization ratios a significantly extended level scheme has been constructed up to spin and parity I π = (19 −) and E x ∼ 6.5 MeV. The experimental results are interpreted within the framework of the gdsh shell model using a realistic effective nucleon-nucleon interaction. Candidates for states with fully aligned angular momenta in the π(d 5/2 , g 7/2) 1 ν(d 5/2 , g 7/2) 5 valence space are identified at 4338 and 5203 keV, as well as in the π(d 5/2 , g 7/2) 1 ν(d 5/2 , g 7/2) 4 h 1 11/2 space at 6087, 6573 and 6783 keV.
High-spin states, lifetime measurements and isomers in 181Os
Nuclear Physics A, 2003
The level scheme of 181 76 Os has been investigated with the 150 Nd(36 S,5n) reaction. The low-K rotational bands built upon the 9/2 + [624], 7/2 − [514] and 1/2 − [521] neutron configurations have been extended and other new bands established. The configurations of these low-K bands are discussed within the framework of the cranked-shell model. The lifetimes for some of the states in the 9/2 + [624] and 1/2 − [521] collective rotational bands were also measured using the Doppler Shift Attenuation method. The large deformations deduced are found to be consistent with those predicted from theoretical Total Routhian Surface calculations. These results support the idea that for these low-K states the nuclear shape is axially symmetric and allows the K quantum number to be defined and the associated K-selection rule to be upheld. This behaviour apparently contrasts with that of the higher-K states in 181 Os. In the higher-spin regime, two new high-K intrinsic states, with K π = 37/2 + and K π = 41/2 + , were established, along with the fragmented decay of a K π = 33/2 − intrinsic state. The configurations and excitation energies of these experimentally determined intrinsic states are found to be in excellent agreement with theoretical calculations based on a fixed shape Nilsson model plus BCS pairing. The structures on top of these intrinsic states do, however, show very different behaviour. A relatively regular high-K rotational band was observed on top of the K π = 41/2 + state but not for the other newly-established intrinsic states. Theoretical configuration-constrained potential energy surface calculations suggest that the irregular transition sequence above the K π = 37/2 + intrinsic bandhead state, the limited excitations observed above the other intrinsic states and the observation of fragmented and non-hindered decays, are due to these configurations being subject to an appreciable γ softness. These calculations reveal that the K π = 41/2 + configuration is less susceptible to distortions in the γ plane than any of the other high-K states.
Physical Review C, 2012
Five N = 82 isotones have been produced in two fusion-fission reactions and their γ rays studied with the Euroball array. The high-spin states of 139 La have been identified for the first time, while the high-spin yrast and near-to-yrast structures of the four others have been greatly extended. From angular correlation analysis, spin values have been assigned to some states of 136 Xe and 137 Cs. Several cascades involving γ rays of 139 La have been found to be delayed, they deexcite an isomeric state with T 1/2 = 315(35) ns located at 1800-keV excitation energy. The excited states of these five N = 82 isotones are expected to be due to various proton excitations involving the three high-j subshells located above the Z = 50 shell closure. This is confirmed by the results of shell-model calculations performed in this work. In addition, high-spin states corresponding to the excitation of the neutron core have been unambiguously identified in 136 Xe, 137 Cs, and 138 Ba.
In-beam spectroscopy of medium-and high-spin states in 133 Ce
Medium and high-spin states in 133 Ce were investigated using the 116 Cd(22 Ne, 5n) reaction and the Gammasphere array. The level scheme was extended up to an excitation energy of ∼22.8 MeV and spin 93/2. Eleven bands of quadrupole transitions and two new dipole bands are identified. The connections to low-lying states of the previously known, high-spin triaxial bands were firmly established, thus fixing the excitation energy and, in many cases, the spin parity of the levels. Based on comparisons with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant density functional theory, it is shown that all observed bands are characterized by pronounced triaxiality. Competing multiquasiparticle configurations are found to contribute to a rich variety of collective phenomena in this nucleus.
Band structures of the 123Cs nucleus
The European Physical Journal A, 2004
Band structures of the 123 Cs nucleus have been investigated using the 100 Mo(28 Si, p4n) reaction at a beam energy of 130 MeV. The previously observed rotational bands based on πh 11/2 , πg 7/2 and πg 9/2 orbitals have been extended. The excitation energies of these bands have been established with the help of interband transitions and those connecting to the low-energy levels established from the β + /EC decay of 123 Ba (T 1/2 = 2.7 m). The bandhead of the πg 9/2 band at the 328.1 keV (I π = 9/2 +) is proposed to be isomeric following arguments based on the intensity balance of the feeding and de-exciting γ transitions. New multiquasiparticle bands based on πh 11/2 ⊗ νh 11/2 ⊗ νg 7/2 , πg 7/2 ⊗ π(h 11/2) 2 and πg 7/2 ⊗ π(h 11/2) 2 ⊗ ν(h 11/2) 2 configurations have been identified. PACS. 21.10.Re Collective levels-23.20.Lv γ transitions and level energies-21.60.-n Nuclear strucutre models and methods-27.60.+j 90 ≤ A ≤ 149
High-spin structures of 51 121, 123, 125, 127 Sb nuclei: Single proton and core-coupled states
European Physical Journal A, 2005
The 121,123,125,127Sb nuclei have been produced as fission fragments in three reactions induced by heavy ions: 12C + 238U at 90 MeV bombarding energy, 18O + 208Pb at 85 MeV, and 31P + 176Yb at 152 MeV. Their level schemes have been built from gamma rays detected using the EUROBALL III and IV arrays. High-spin states of 123,125,127Sb nuclei have been identified for the first time. Moreover isomeric states lying around 2.3 MeV have been established in 123,125,127Sb from the delayed coincidences between the fission fragment detector SAPhIR and the gamma array. All the observed states can be described by coupling a d 5/2 or g 7/2 proton to an excited Sn core involving either vibrational states or broken neutron pairs.