Title: Spherical coupled-cluster theory for open-shell nuclei

Abstract

A microscopic description of nuclei is important to understand the nuclear shell model from fundamental principles. This is difficult to achieve for more than the lightest nuclei without an effective approximation scheme. Define and evaluate an approximation scheme that can be used to study nuclei that are described as two particles attached to a closed (sub-)shell nucleus. The equation-of-motion coupled-cluster formalism has been used to obtain ground- and excited-state energies. This method is based on the diagonalization of a non-Hermitian matrix obtained from a similarity transformation of the many-body nuclear Hamiltonian. A chiral interaction at the next-to-next-to-next-to leading order (N³LO) using a cutoff at 500 MeV was used. The ground-state energies of ⁶Li and ⁶He were in good agreement with a no-core shell-model calculation using the same interaction. Several excited states were also produced with overall good agreement. Only the $J^π = 3^+$ excited state in ⁶Li showed a sizable deviation. The ground-state energies of ¹⁸O, ¹⁸F, and ¹⁸Ne were converged but underbound compared to experiment. Moreover, the calculated spectra were converged and comparable to both experiment and shell-model studies in this region. Some excited states in ¹⁸O were high or missing in the spectrum. It was also shown thatmore » the wave function for both ground and excited states separates into an intrinsic part and a Gaussian for the center-of-mass coordinate. Spurious center-of-mass excitations are clearly identified. Results are converged with respect to the size of the model space and the method can be used to describe nuclear states with simple structure. Especially the ground-state energies were very close to what has been achieved by exact diagonalization. To obtain a closer match with experimental data, effects of three-nucleon forces, the scattering continuum, as well as additional configurations in the coupled-cluster approximations are necessary.« less

Authors:

Jansen, G. R. ^[1]

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+ Show Author Affiliations

1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Oslo (Norway). Dept. of Physics and Center of Mathematics for Applications

Publication Date:

Mon Aug 05 00:00:00 EDT 2013

Research Org.:

Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1565057

Grant/Contract Number:  

AC05-00OR22725; FG02-96ER40963; SC0008499

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review C, Nuclear Physics

Additional Journal Information:

Journal Volume: 88; Journal Issue: 2; Journal ID: ISSN 0556-2813

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Physics