Nuclear Theory·nucl-th

Wednesday·October 28, 2015

10 papers—7 primary·3 cross-listed

01
$^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ astrophysical $S$ factors from the no-core shell model with continuum
Jérémy Dohet-Eraly🇨🇦 · Petr Navrátil🇨🇦 · Sofia Quaglioni🇺🇸 · Wataru Horiuchi🇯🇵 · Guillaume Hupin🇺🇸 · Francesco Raimondi🇨🇦
The $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ astrophysical $S$ factors are calculated within the no-core shell model with continuum using a renormalized chiral nucleon-nucleon interaction. The $^{3} He (α, γ)^{7} Be$ astrophysical $S$ factors agree reasonably well with the experimental data while the $^{3} H (α, γ)^{7} Li$ ones are overestimated. The seven-nucleon bound and resonance states and the $α +^{3} He /^{3} H$ elastic scattering are also studied and compared with experiment. The low-lying resonance properties are rather well reproduced by our approach. At low energies, the $s$ -wave phase shift, which is non-resonant, is overestimated.
nucl-thastro-ph.SRnucl-exPLB(2016)·82 citations
02
Gauge Symmetry in the Large-amplitude Collective Motion of Superfluid Nuclei
Koichi Sato
The adiabatic self-consistent collective coordinate (ASCC) method is a practical method for the description of large-amplitude collective motion in atomic nuclei with superfluidity and an advanced version of the adiabatic time-dependent Hartree-Fock-Bogoliubov theory. We investigate the gauge symmetry in the ASCC method on the basis of the theory of constrained systems. The gauge symmetry in the ASCC method is originated from the constraint on the particle number in the collective Hamiltonian, and it is partially broken by the adiabatic expansion. The validity of the adiabatic expansion under the general gauge transformation is also discussed.
nucl-thcond-mat.quant-gasPTEP(2015)·5 citations
03
Fission dynamics within time-dependent Hartree-Fock: boost-induced fission
P. M. Goddard · P. D. Stevenson · A. Rios
Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide $^{240}$ Pu as an example. Methods: Quadrupole constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickly absorbed by the nucleus. In instantaneous boosts, this leads to fast shape rearrangements and violent dynamics that can ultimately lead to fission. This is a qualitatively different process than the deformation-induced fission. Boosts induced within a finite time window excite the system in a relatively gentler way, and do induce fission but with a smaller energy deposition. Conclusions: The fission products obtained using boost-induced fission in time-dependent Hartree-Fock are more asymmetric than the fragments obtained in deformation-induced fission, or the corresponding adiabatic approaches.
nucl-thPRC(2016)·56 citations
04
The influence of the Coulomb exchange term on nuclear single-proton resonances
Shu-Yang Wang · Zhong-Lai Zhu · Zhong-Ming Niu
Nuclear single-proton resonances are sensitive to the Coulomb field, while the exchange term of Coulomb field is usually neglected due to its nonlocality. By combining the complex scaling method with the relativistic mean-field model, the influence of the Coulomb exchange term on the single-proton resonances is investigated by taking Sn isotopes and $N = 82$ isotones as examples. It is found that the Coulomb exchange term reduces the single-proton resonance energy within the range of $0.4 - 0.6$ MeV, and lead to similar isotopic and isotonic trends of the resonance energy as those without the Coulomb exchange term. Moreover, the single-proton resonance width is also reduced by the Coulomb exchange term, whose influence generally decreases with the increasing neutron number and increases with the increasing proton number. However, the influence of the Coulomb exchange term cannot change the trend of the resonance width with respect to the neutron number and proton number. Furthermore, the influence of the Coulomb exchange term on the resonance width is investigated for the doubly magic nuclei $^{40}$ Ca, $^{56, 78}$ Ni, $^{100, 132}$ Sn, and $^{208}$ Pb. It is found that the Coulomb exchange term reduces the proton resonance width within $0.2$ MeV, whose magnitude depends on the specific nucleus and the quantum numbers of resonant states.
nucl-thnucl-exNucl.Sci.Tech.(2016)·6 citations
05
Implication of the proton-deuteron radiative capture for Big Bang Nucleosynthesis
L.E. Marcucci · G. Mangano · A. Kievsky · M. Viviani
The astrophysical $S$ -factor for the radiative capture $d (p, γ)^{3}$ He in the energy-range of interest for Big Bang Nucleosynthesis (BBN) is calculated using an {\it ab-initio} approach. The nuclear Hamiltonian retains both two- and three-nucleon interactions - the Argonne $v_{18}$ and the Urbana IX, respectively. Both one- and many-body contributions to the nuclear current operator are included. The former retain for the first time, besides the $1/ m$ leading order contribution ( $m$ is the nucleon mass), also the next-to-leading order term, proportional to $1/ m^{3}$ . The many-body currents are constructed in order to satisfy the current conservation relation with the adopted Hamiltonian model. The hyperspherical harmonics technique is applied to solve the $A = 3$ bound and scattering states. A particular attention is used in this second case in order to obtain, in the energy range of BBN, an uncertainty on the astrophysical $S$ -factor of the order or below $\sim$ 1 %. Then, in this energy range, the $S$ -factor is found to be $\sim$ 10 % larger than the currently adopted values.Part of this increase (1-3 %) is due to the $1/ m^{3}$ one-body operator, while the remaining is due to the new more accurate scattering wave functions. We have studied the implication of this new determination for the $d (p, γ)^{3}$ He $S$ -factor on deuterium primordial abundance. We find that the predicted theoretical value for $^{2}$ H/H is in excellent agreement with its experimental determination, using the most recent determination of baryon density of Planck experiment, and with a standard number of relativistic degrees of freedom $N_{eff} = 3.046$ during primordial nucleosynthesis.
nucl-thastro-ph.COPRL(2016)·107 citations
06
Covariant density functional theory: Reexamining the structure of superheavy nuclei
S. E. Agbemava · A. V. Afanasjev · T. Nakatsukasa · P. Ring
A systematic investigation of even-even superheavy elements in the region of proton numbers $100 \leq Z \leq 130$ and in the region of neutron numbers from the proton-drip line up to neutron number $N = 196$ is presented. For this study we use five most up-to-date covariant energy density functionals of different types, with a non-linear meson coupling, with density dependent meson couplings, and with density-dependent zero-range interactions. Pairing correlations are treated within relativistic Hartree-Bogoliubov (RHB) theory based on an effective separable particle-particle interaction of finite range and deformation effects are taken into account. This allows us to assess the spread of theoretical predictions within the present covariant models for the binding energies, deformation parameters, shell structures and $α$ -decay half-lives. Contrary to the previous studies in covariant density functional theory, it was found that the impact of $N = 172$ spherical shell gap on the structure of superheavy elements is very limited. Similar to non-relativistic functionals some covariant functionals predict the important role played by the spherical $N = 184$ gap. For these functionals (NL3*, DD-ME2 and PC-PK1), there is a band of spherical nuclei along and near the $Z = 120$ and $N = 184$ lines. However, for other functionals (DD-PC1 and DD-ME $δ$ ) oblate shapes dominate at and in the vicinity of these lines. Available experimental data are in general described with comparable accuracy and do not allow to discriminate these predictions.
nucl-thPRC(2015)·102 citations
07
Microscopic modeling of mass and charge distributions in the spontaneous fission of 240Pu
Jhilam Sadhukhan · Witold Nazarewicz · Nicolas Schunck
In this letter, we outline a methodology to calculate microscopically mass and charge distributions of spontaneous fission yields. We combine the multi-dimensional minimization of collective action for fission with stochastic Langevin dynamics to track the relevant fission paths from the ground-state configuration up to scission. The nuclear potential energy and collective inertia governing the tunneling motion are obtained with nuclear density functional theory in the collective space of shape deformations and pairing. We obtain a quantitative agreement with experimental data and find that both the charge and mass distributions in the spontaneous fission of 240Pu are sensitive both to the dissipation in collective motion and to adiabatic characteristics.
nucl-thPRC(2016)·86 citations

Affiliations

first authorsco-authorsvia INSPIRE

3He(α,γ)7Be and 3H(α,γ)7Li astrophysical S factors from the no-core shell model with continuum

Gauge Symmetry in the Large-amplitude Collective Motion of Superfluid Nuclei

Fission dynamics within time-dependent Hartree-Fock: boost-induced fission

The influence of the Coulomb exchange term on nuclear single-proton resonances

Implication of the proton-deuteron radiative capture for Big Bang Nucleosynthesis

Covariant density functional theory: Reexamining the structure of superheavy nuclei

Microscopic modeling of mass and charge distributions in the spontaneous fission of 240Pu

Affiliations

$^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ astrophysical $S$ factors from the no-core shell model with continuum