Intrinsic and Rotational Level Structures in Odd-Odd Actinides

Masses of superheavy (SH) nuclei with Z = 98−128, including odd and odd-odd nuclei, are systematically calculated within the microscopic-macroscopic model based on the deformed Woods-Saxon potential. Ground states are found by minimizing energy over deformations and configurations. Pairing in odd particle-number systems is treated either by blocking or by adding the BCS energy of the odd quasiparticle. Three new parameters are introduced which may be interpreted as the constant mean pairing energies for even-odd, odd-even and odd-odd nuclei. They are adjusted by a fit to masses of heavy nuclei. Other parameters of the model, fixed previously by fitting masses of even-even heavy nuclei, are kept unchanged. With this adjustment, the masses of SH nuclei are predicted and then used to calculate α-decay energies to be compared to known measured values. It turns out that the agreement between calculated Qα values with data in SH nuclei is better than in the region of the mass fit. The model overestimates Qα for Z = 111 − 113. Ground state (g.s.) configurations in some SH nuclei hint to a possible α-decay hindrance. The calculated configurationpreserving transition energies show that in some cases this might explain discrepancies, but more data is needed to explain the situation.

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“…, were extracted [28,29]. The former are usually less than 50 keV, while the latter amount to 100-300 keV.…”

Section: A Odd-odd Nucleimentioning

confidence: 99%

Qαvalues in superheavy nuclei from the deformed Woods-Saxon model

2014

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“…This formulation has been effectively employed to describe, and to predict, the location and character of 2qp bands, in particular the frequently occurring long-lived isomer pairs of several odd-odd actinides ranging from 93 Np through 101 Md [20][21][22][23][24][25][26][27]. Exhaustive data on 2qp bands and associated rotational levels of the actinides [16] and the rare-earth nuclei [28,29] have since been presented in a series of review articles, wherein a semiempirical version of the earlier formulation is introduced. Very recently, we have reported [30][31][32] the results of our analysis for level structures, including characterization of isomer pairs, in n-rich Pm (Z = 63) odd-odd isotopes; the procedure adopted therein is employed here as well.…”

Section: Model Formulation and Calculationmentioning

confidence: 98%

“…In principle the model parameters (e.g., E GM , 2 /2I, E N , etc) can be evaluated theoretically [15,35]. But in the semiempirical approach adopted here [16,[28][29][30][31][32] we use the experimental data in any odd-odd neighbor wherein a specific 2qp band, expected in 240 Np, has been experimentally identified. These experimental data are then used as inputs to deduce the parameters for respective structures, to be used in Eqs.…”

Section: Model Formulation and Calculationmentioning

confidence: 98%

“…As our second step, we identify the physically admissible 2qp bands in 240 Np within the energy range constrained by the fact that the 240 U decay, which populates 240 Np low-spin levels, has Q β = 390(17) keV [34]. Results of this exercise for 240 Np are presented in Table I using the following expression [16,28]:…”

Section: Model Formulation and Calculationmentioning

confidence: 99%

“…In Sec. III, we outline our three-step procedure involving (a) mapping of the available experimental single particle (1qp) configuration space, (b) enumeration of the physically admissible 2qp bands in the deformed odd-odd 240 93 Np 147 nucleus as GM doublets in accordance with the Gallagher-Moszkowski (GM) spin-spin coupling rule [14], and (c) evaluating respective 2qp band-head energies using the rotor particle model with inclusion of residual n-p interaction contribution [15,16]. These calculated level energies, together with our level-by-level analysis of 23 β populated levels in 240 Pu are then used in Sec.…”

Section: Introductionmentioning

confidence: 99%

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Level structures inNp240

2014

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Whereas the 7.2 min 240 Np, first identified over 60 years ago, has been assigned conflicting configuration by various investigators, the 62 min 240 Np is assigned a "probable" configuration, deduced in each case by primarily focusing on just a single β-connected pair of levels in either 240 Np (β − ) 240 Pu or 240 U (β − ) 240 Np decay. We evaluate the level energies of physically admissible 2qp configurations in 240 93 Np 147 employing a three-step procedure, with experimental inputs at each step, and using a well tested two-particle rotor model with inclusion of residual n-p interaction and other contributions. This exercise clearly establishes that the 62 min 240 Np and the 7.2 min 240 Np isomers constitute a Gallagher-Moszkowski (GM) doublet corresponding to the two-quasiparticle (2qp) configuration 5 + {p5/2 + [642] ± n5/2 + [622]}0 + with J π K = 1 + 0 for the higher-lying 7.2 min isomer. This assignment is conclusively confirmed in a level-by-level analysis of data on 23 β transitions in these decays.Structures of a few other 240 Np levels populated in 240 U β decay are also discussed.

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