Nuclear Theory·nucl-th

Wednesday·May 29, 2019

11 papers—5 primary·6 cross-listed

01
Quadrupole dominance in light Cd and Sn isotopes
A.P. Zuker🇫🇷
Shell model calculations with the neutron effective charge as single free parameter describe well the \bet and \bef rates for $N \leq 64$ in the Cd and Sn isotopes. The former exhibit weak permanent deformation corroborating the prediction of a pseudo SU3 symmetry, which remains of heuristic value in the latter, though the pairing force erodes the quadrupole dominance. Calculations in $1 0^{7}$ and $1 0^{10}$ -dimensional spaces exhibit almost identical patterns: A vindication of the shell model. For $N \geq 64$ quadrupole dominance is accentuated in the Cd isotopes and gives way to seniority dominance for the Sn isotopes.
nucl-thnucl-ex2 citations
02
Rotational excitations in near neutron-drip line nuclei: the birth and death of particle-bound rotational bands and the extension of nuclear landscape beyond spin zero neutron drip line
A. V. Afanasjev · N. Itagaki · D. Ray
Two new mechanisms active in rotating nuclei located in the vicinity of neutron drip line have been discovered. Strong Coriolis interaction acting on high- $j$ orbitals transforms particle-unbound (resonance) nucleonic configurations into particle-bound ones with increasing angular momentum. The point of the transition manifests the birth of particle-bound rotational bands. Alternative possibility of the transition from particle-bound to resonance rotational band (the death of particle-bound rotational bands) with increasing spin also exists but it is less frequent in the calculations. The birth of particle-bound rotational bands provides a mechanism for the extension of nuclear landscape to neutron numbers which are larger than those of the neutron drip line in non-rotating nuclei.
nucl-thPLB(2019)·8 citations
03
Superheavy nuclei in microscopic collective Hamiltonian approach: the impact of beyond mean field correlations on the ground state and fission properties
Z. Shi · A. V. Afanasjev · Z. P. Li · J. Meng
The impact of beyond mean field effects on the ground state and fission properties of superheavy nuclei has been investigated in a five-dimensional collective Hamiltonian based on covariant density functional theory. The inclusion of dynamical correlations reduces the impact of the $Z = 120$ shell closure and induces substantial collectivity for the majority of the $Z = 120$ nuclei which otherwise are spherical at the mean field level (as seen in the calculations with the PC-PK1 functional). Thus, they lead to a substantial convergence of the predictions of the functionals DD-PC1 and PC-PK1 which are different at the mean field level. On the contrary, the predictions of these two functionals remain distinctly different for the $N = 184$ nuclei even when dynamical correlations are included. These nuclei are mostly spherical (oblate) in the calculations with PC-PK1 (DD-PC1). Our calculations for the first time reveal significant impact of dynamical correlations on the heights of inner fission barriers of superheavy nuclei with soft potential energy surfaces, the minimum of which at the mean field level is located at spherical shape. These correlations affect the fission barriers of the nuclei, which are deformed in the ground state at the mean field level, to a lesser degree.
nucl-thPRC(2019)·33 citations
04
Bayesian updating for data adjustments and multi-level uncertainty propagation within Total Monte Carlo
E. Alhassan · D. Rochman · H. Sjöstrand · A. Vasiliev · A.J. Koning · H. Ferroukhi
In this work, a method is proposed for combining differential and integral benchmark experimental data within a Bayesian framework for nuclear data adjustments and multi-level uncertainty propagation using the Total Monte Carlo method. First, input parameters to basic nuclear physics models implemented within the state of the art nuclear reactions code, TALYS, were sampled from uniform distributions and randomly varied to produce a large set of random nuclear data files. Next, a probabilistic data assimilation was carried out by computing the likelihood function for each random nuclear data file based first on only differential experimental data (1st update) and then on integral benchmark data (2nd update). The individual likelihood functions from the two updates were then combined into a global likelihood function which was used for the selection of the final 'best' file. The proposed method has been applied for the adjustment of $^{208}$ Pb in the fast neutron energy region below 20 MeV. The 'best' file from the adjustments was compared with available experimental data from the EXFOR database as well as evaluations from the major nuclear data libraries and found to compare favourably.
nucl-th1 citation
05
Consistency of two different approaches to determine the strength of a pairing residual interaction in the rare-earth region
Nurhafiza M. Nor🇲🇾 · Nor-Anita Rezle🇲🇾 · Kai-Wen Kelvin-Lee🇲🇾 · Meng-Hock Koh🇲🇾 · L. Bonneau🇫🇷 · P. Quentin🇻🇳
Two fits of the pairing residual interaction in the rare-earth region are independently performed. One is made on the odd-even staggering of masses by comparing measured and explicitly calculated three-point binding-energy differences centered on odd-even nuclei. Another deals with the moments of inertia of the first 2+ states of well deformed even-even nuclei upon comparing experimental data with the results of Inglis-Belyaev moments (supplemented by a crude estimate of the so-called Thouless-Valatin corrections). The sample includes 24 even-even and 31 odd-mass nuclei selected according to two criteria: they should have good rotor properties and should not correspond to low pairing-correlation regimes in their ground states. Calculations are performed in the self-consistent Hartree-Fock plus BCS framework (implementing a self-consistent blocking in the case of odd-mass nuclei). The Skyrme SIII parametrization is used in the particle-hole channel and the fitted quantities are the strengths of |Tz|=1 proton and neutron seniority residual interactions. As a result, the two fits yield sets of strengths in excellent agreement: about 0.1% for the neutron parameters and 0.2% for protons. In contrast when one performs such a fit on odd-even staggering from quantities deduced from BCS gaps or minimal quasiparticle energies in even-even nuclei, as is traditional, one obtains results significantly different from those obtained in the same nuclei by a fit of moments of inertia. As a conclusion, beyond providing a phenomenological tool for microscopic calculations in this region, we have illustrated the proposition made in the seminal paper of Bohr, Mottelson and Pines that moments of inertia and odd-even staggering in selected nuclei were excellent measuring sticks of nuclear pairing correlations.
nucl-thPRC(2019)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE

Quadrupole dominance in light Cd and Sn isotopes

Rotational excitations in near neutron-drip line nuclei: the birth and death of particle-bound rotational bands and the extension of nuclear landscape beyond spin zero neutron drip line

Superheavy nuclei in microscopic collective Hamiltonian approach: the impact of beyond mean field correlations on the ground state and fission properties

Bayesian updating for data adjustments and multi-level uncertainty propagation within Total Monte Carlo

Consistency of two different approaches to determine the strength of a pairing residual interaction in the rare-earth region

Affiliations