nucl-th digest · Sep 8, 2023

[Submitted on 7 Sept 2023]

Covariant density functional theory for nuclear fission based on two-center harmonic oscillator basis

Zeyu Li · Shengyuan Chen · Minghui Zhou · Yongjing Chen · Zhipan Li

Nowdays, modern microscopic approaches for fission are generally based on the framework of nuclear density functional theory (DFT), which has enabled a self-consistent treatment of both static and dynamic aspects of fission. The key issue is a DFT solver with high precision and efficiency especially for the large elongated configurations. Purpose: To develope a DFT solver with high precision and efficiency based on the point coupling covariant density functional theory (CDFT), which has achieved great success in describing properties of nuclei for the whole nuclear chart. Method: We have extended the point-coupling CDFT to be based on the two-center harmonic oscillator (TCHO) basis, which matches well with the large elongated configurations during the fission process. Multi-dimensional constraint and time-dependent generator coordinate method (TDGCM) have been used to analyze the fission potential energy surface and fission dynamics, respectively. To simulate the splitting process of the nascent fragments beyond scission, we also introduce a density constraint into the new CDFT framework. Results: Illustrative calculations have been done for the PESs and induced fission dynamics of two typical examples: $^{226}$ Th and $^{240}$ Pu. A more reasonable PES is obtained in the new framework compared to that based on the once-center harmonic oscillator (OCHO) with the same basis space. An optimization of about $0.2 \sim 0.3$ MeV has been achieved for the outer fission barriers and large elongated configurations. The dynamical simulations based on TCHO basis presents a trend to improve the description for fission yields. Conclusions: The new developed CDFT solver optimizes the elongated configurations, improves the calculation efficiency, and provides a basis for large-scale multi-dimensional constraint calculations and dynamical simulations.

Subjects:: Nuclear Theory (nucl-th)
arXiv:: 2309.03461 [pdf]

PRC(2024)·7 citations

Universality of

nn

distributions of

s

-wave

2 n

halos and the unitary limit

We calculate neutron-neutron relative-energy distributions of

s

-wave two-neutron (

2 n

) halo nuclei using Halo Effective Field Theory (Halo EFT) at leading order. At this order these systems are described by the

2 n

separation energy, the neutron-core (

n c

) virtual-state energy and the neutron-neutron (

nn

) scattering length. We focus on knockout reactions where the removal of the core is sudden, such that the final-state interactions are dominated by the

nn

interaction. We consider the neutron relative-energy distribution for the nuclei

^{11}

Li,

^{14}

Be,

^{17}

^{19}

B, and

^{22}

C. We show that the ground-state neutron momentum distributions of all these nuclei stem from a single curve, which can be obtained by taking both the neutron-core and neutron-neutron interaction to the unitary limit. This universal description can be extended to the final distribution measured in experiment by including

nn

final-state interactions via the approximate technique of enhancement factors. For all the nuclei considered we find good agreement between the full leading-order Halo EFT calculation and the universal prediction obtained in this way. The universality of the ground-state momentum distribution in two-neutron Borromean halos can thus be tested by dividing the experimental results from sudden core knockout by the enhancement factor and comparing to the unitary-limit prediction.

Comments:: 10 pages, 5 figures
Subjects:: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:: 2309.03902 [pdf]

PRC(2024)·2 citations

Friday·September 8, 2023

Covariant density functional theory for nuclear fission based on two-center harmonic oscillator basis

Universality of $nn$ distributions of $s$ -wave $2 n$ halos and the unitary limit

Affiliations

Covariant density functional theory for nuclear fission based on two-center harmonic oscillator basis

Universality of nn distributions of s-wave 2n halos and the unitary limit

Affiliations

Universality of $nn$ distributions of $s$ -wave $2 n$ halos and the unitary limit