Coupling of Angular Momenta in Two-Particle States in Deformed Even-Even Nuclei

Gallagher, Charles J.

doi:10.1103/physrev.126.1525

Cited by 84 publications

(29 citation statements)

References 15 publications

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“…[22]. These results are in qualitative agreement with expectations based on the Gallagher rule [43]. After correcting for zero-point energy E 0 = 8h 2 /2J (1) , that is, E 0 = 49 keV (51 keV) for 252 No ( 250 Fm) as inferred from the kinematic moments of inertia J (1) shown in Fig.…”

Section: Theoretical Frameworksupporting

confidence: 88%

“…It is interesting to note that these values are very close to the asymptotic limit for singlet states ( = 0) which are energetically favored according to the Gallagher rule [43]. In this case the gyromagnetic factor of the spin cancels and one has only a contribution from the angular momentum I of the two protons (g K = g γ -ray branching ratio, the g K factor, and decay probabilities was used, i.e.,…”

Section: Spin Assignmentmentioning

confidence: 82%

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Investigation of high-Kstates in252No

Sulignano¹,

Theisen²,

Delaroche³

et al. 2012

Phys. Rev. C

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Section: Theoretical Frameworksupporting

confidence: 88%

Section: Spin Assignmentmentioning

confidence: 82%

Investigation of high-Kstates in252No

Sulignano¹,

Theisen²,

Delaroche³

et al. 2012

Phys. Rev. C

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“…− configuration has parallel intrinsic-spin coupling, which is energetically unfavoured according to the Gallagher rules [24], and the final K π = 6 − energy could be ≈0.2 MeV higher than the 1.59 MeV given in Table I. On that assumption, it remains the lowest-energy two-quasiparticle excitation, apart from its favored K π = 1 − (K = 1 − 2 ) partner, and isomerism can be expected.…”

mentioning

confidence: 92%

High-Kisomers in neutron-rich zirconium isotopes

2012

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The neutron-rich zirconium isotopes are a key testing ground for nuclear models due to their sensitivity to shape changes, and because they cross the r-process path of explosive nucleosynthesis. Furthermore, recent experimental data have revealed a high-spin isomer in 108 Zr. Here we report the results of configuration-constrained potential-energy-surface calculations of ground states and high-K states in [104][105][106][107][108][109][110] Zr, restricted to quadrupole and hexadecapole shapes. These calculations enable the existing isomer data to be understood, and predictions are made for 110 Zr. The zirconium (Z = 40) isotopes are well known [1] for their variety of shapes, with considerable sensitivity to the neutron number, which is at least partly a consequence of the Z = 40 subshell gap in single-particle energies. On the neutron-rich side of stability, the shape sensitivity extends into the landscape of rapid-neutron-capture, r-process nucleosynthesis relevant to supernova detonations, giving an added incentive to understand the nuclear structure. In the past decade there have been many theoretical studies related to this theme (see for example Refs. [2-9]), but only Xu et al. [2], albeit with a more phenomenological approach, have given detailed predictions of isomeric states in the neutron-rich even-even zirconium isotopes. Now, with the success of the RIKEN RIBF accelerator complex, major experimental advances have been possible, extending knowledge of these isotopes [10,11]. One of the notable nuclear structure features was the discovery [11] of an isomer in 108 Zr, but not in 106 Zr or 104 Zr. The isomer in 108 Zr was tentatively interpreted as being due a tetrahedral shape, which has been predicted to be most favored in 110 Zr [12], though the excited-state structure of that isotope has not yet itself been studied experimentally. In the present work, we extend the earlier configuration-constrained potential-energysurface (PES) calculations for this region [2], now focused on even-even [104][105][106][107][108][109][110] Zr. We consider the quadrupole (β 2 and γ ) and hexadecapole (β 4 ) deformations as the relevant degrees of freedom, and show that the existing data can be understood on this basis. We also predict the low-lying two-quasiparticle structure of 110 Zr. The configuration-constrained PES model [13] has been widely used in various mass regions, including the superheavy [14,15] and drip-line [16] regions, to calculate the energies and shapes of high-K states, where K is the projection of the angular momentum on the nuclear axis of symmetry. High-K states at low excitation energy are often associated with isomerism, due to the K-forbidden nature of their decays * p.walker@surrey.ac.uk [17]. In the model, single-particle levels are obtained from the Woods-Saxon potential with the set of universal parameters [18]. For the pairing correlations, particle-number projection is approximated by the Lipkin-Nogami technique [19], with the pairing strength determined by the average-gap method [20]. ...

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“…The interaction leads to splitting of the spin-antiparallel coupling and the spin-parallel coupling. The former is usually lower in energy for two quasineutrons or two quasiprotons, while it is higher in energy for the configuration with a quasineutron and a quasiproton, which is known as the Gallagher-Moszkowski (GM) rule [45,46]. In the A ≈ 180 mass region, the splitting energy is in the range of ≈100 to 400 keV [47].…”

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confidence: 99%

Favored configurations for four-quasiparticleKisomerism in the heaviest nuclei

2014

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Configuration-constrained potential-energy-surface calculations are performed including β 6 deformation to investigate high-K isomeric states in nuclei around 254 No and 270 Ds, the heaviest nuclei where there have been some observations of two-quasiparticle isomers, while data for four-quasiparticle isomers are scarce. We predict the prevalent occurrence of four-quasiparticle isomeric states in these nuclei, together with their favored configurations. The most notable examples, among others, are K π = 20 + states in 266,268 Ds and 268,270 Cn having very high K value, relatively low excitation energy, and well-deformed axially symmetric shape. The predicted isomeric states, with hindered spontaneous fission and α decay, could play a significant role in the future study of superheavy nuclei. One of the important endeavors in current nuclear-structure studies is to extend the nuclide landscape towards the predicted island of stability of superheavy nuclei and beyond, which will provide us with knowledge about the end of the periodic table of elements, the heaviest magic numbers in nuclei, and the nuclear mass limit [1,2]. When going far away from 208 Pb towards the expected superheavy doubly magic nucleus, nuclear shape significantly deviates from spherical symmetry. The nuclei around 254 No and 270 Ds are predicted to be well deformed with non-negligible higher-order deformation such as β 6 [3][4][5][6]. Modern spectroscopy experiments (see Refs. [7][8][9] and references therein) have been able to study these nuclei in detail. Together with various model calculations (see, e.g., Refs. [10-27]), such studies of collective and singleparticle excitations result in not only insights into these nuclei themselves but also information for the heavier unknown nuclei due to the contributions of higher-lying single-particle states. Amongst them, multiquasiparticle (multi-qp) isomers associated with axial symmetry and nearly pure Nilsson configurations provide structure information in a very direct way.This type of isomer [28] occurs in axially deformed nuclei through unpaired nucleons occupying single-particle states with high-values ( is the single-particle angular momentum projection onto the symmetry axis). The total angular momentum along the symmetry axis, K, is therefore high, and leads to retardation in γ -ray transitions to low-K states. Since the conservation of the K quantum number is intimately related to axial symmetry, the observations of high-K isomers in nuclei around 254 No and 270 Ds [7] support the predictions of well-developed prolate deformations for the nuclei. These nuclei, with high-orbitals around the Fermi surfaces for both neutrons and protons, are analogous to the A ≈ 180 nuclei and neutron-rich Hf nuclei where not only two-qp but also four-qp (or more) high-K isomers prevail [29][30][31]. Indeed, it has been observed in 254 254 No is so far the unique four-qp isomer known in transfermium nuclei. More could be found with the advance of experimental techniques applicable to the heaviest...

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Coupling of Angular Momenta in Two-Particle States in Deformed Even-Even Nuclei

Cited by 84 publications

References 15 publications

Investigation of high-Kstates in252No

Investigation of high-Kstates in252No

High-Kisomers in neutron-rich zirconium isotopes

Favored configurations for four-quasiparticleKisomerism in the heaviest nuclei

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