Engineering topics
Hjorth-Jensen, M
Publications and source records attributed to Hjorth-Jensen, M.
Toward open-shell nuclei with coupled-cluster theory
We develop a method based on equation-of-motion coupled-cluster theory to describe properties of open-shell nuclei with A{+-}2 nucleons outside a closed shell. We perform proof-of-principle calculations for the ground states of the helium isotopes {sup 3-6}He and the first excited 2{sup +} state in {sup 6}He. The comparison with exact results from matrix diagonalization in small model spaces demonstrates the accuracy of the coupled-cluster methods. Three-particle-one-hole excitations of {sup 4}He play an important role for the accurate description of {sup 6}He. For the open-shell nucleus {sup 6}He, the computational cost of the method is comparable with the coupled-cluster singles-and-doubles approximation while its accuracy is similar to the coupled-cluster with singles, doubles, and triples excitations.
Structure of {sup 60,62}Fe and the onset of {nu}g{sub 9/2} occupancy
Level structures in {sup 60,62}Fe{sub 34,36} and adjacent nuclei were studied with Gammasphere using the reaction of a 430-MeV {sup 64}Ni beam on a 55-mg/cm{sup 2} thick {sup 238}U target. High-spin level schemes were deduced from singly- and doubly-gated prompt coincidence events. Levels populated in the {beta} decay of {sup 60,62}Mn isomers were studied in singly- and doubly-gated delayed coincidences. Spin and parity assignments were deduced from angular correlations of {gamma} rays observed in both nuclei, leading to firm positive-parity yrast assignments up through 8{sup +} in {sup 62}Fe. The observed levels for {sup 60}Fe up to {approx}3.5 MeV compare well with pf shell-model calculations available in the literature. Calculations performed in a limited pfg basis exhibit reasonable agreement for the 2{sup +}, 4{sup +}, and 6{sup +} levels in {sup 62}Fe. However, theoretical descriptions that include the newly identified negative-parity levels in {sup 62}Fe require a much larger basis, necessarily including g{sub 9/2} neutrons, as well as improved interactions leading to negative-parity levels.
Recent Progress in Shell-Model Calculations for pfg-shell Nuclei
The structure of upper pf-shell nuclei is studied by the nuclear shell model, taking a model space consisting of four spherical single-particle orbits p{sub 3/2}, f{sub 5/2}, p{sub 1/2} and g{sub 9/2}. The effective interaction JUN45 is used, which is obtained by modifying empirically the renormalized G-matrix interaction. The oblate-prolate shape coexistence in {sup 68}Se is predicted consistently with the experimental observations, indicating the applicability of the shell model to the cases with moderate deformation. The calculated high-spin band structure highlights the important role played by the g{sub 9/2} orbit. The appearance of the j{sub p}-j{sub n} multiplets in {sup 88}Y is successfully described except for a few cases such as the 1{sub 1}{sup +} state, suggesting the good property of the effective proton-neutron interaction inherited from the renormalized G-matrix.
Ab Initio Computation of the {sup 17}F Proton Halo State and Resonances in A=17 Nuclei
We perform coupled-cluster calculations of the energies and lifetimes of single-particle states around the doubly magic nucleus {sup 16}O based on chiral nucleon-nucleon interactions at next-to-next-to-next-to-leading order. To incorporate effects from the scattering continuum, we employ a Gamow-Hartree-Fock basis. Our calculations for the J{sup {pi}=}1/2{sup +} proton halo state in {sup 17}F and the 1/2{sup +} state in {sup 17}O agree well with experiment, while the calculated spin-orbit splitting between 5/2{sup +} and 3/2{sup +} states is too small due to the lack of three-nucleon forces. Continuum effects yield a significant amount of additional binding energy for the 1/2{sup +} and 3/2{sup +} states in {sup 17}O and {sup 17}F.