Nuclear structure studies for the astrophysical r-process

Nuclear Data Sheets for A = 131

Nuclear Data Sheets for A = 133

The focus of the present review is the production of the heaviest elements in nature via the r-process. A correct understanding and modeling requires the knowledge of nuclear properties far from stability and a detailed prescription of the astrophysical environment. Experiments at CERN/ISOLDE have played a pioneering role in exploring the characteristics of nuclear structure in terms of masses and β-decay properties. Initial examinations paid attention to far unstable nuclei with magic neutron numbers related to r-process peaks, while present activities are centered on the evolution of shell effects with the distance from the valley of stability. We first show in site-independent applications the effect of both types of nuclear properties on r-process abundances. Then, we explore the results of calculations related to two different “realistic”astrophysical sites, (i) the supernova neutrino wind and (ii) neutron star mergers. We close with a list of remaining theoretical and experimental challenges needed to overcome for a full understanding of the nature of the r-process, and the role CERN/ISOLDE can play in this process.

/pdf/nuclear-structure-studies-at-isolde-and-their-impact-on-the-4f2gtjsfg4.pdf

Nuclear structure studies at ISOLDE and their impact on the astrophysical r-process

A collective S and D nucleon pair approximation of the shell model is applied to even-even Sn, Te, Xe, Ba, and Ce isotopes with mass number A ∼120–150 and neutron number ranging from 74 to 90. Our Hamiltonian employs monopole pairing, quadrupole pairing plus quadrupole-quadrupole-type interactions between like valence nucleons and quadrupole-quadrupole interactions between valence neutrons and valence protons. With very few parameters, the low-lying states of even-even Sn, Te, Xe, Ba, and Ce isotopes are well described. The calculated B(E2) values and g factors are consistent with recent experimental data. Our systematic calculations also predict B(E2) values and g factors (in particular, for nuclei with valence neutrons in the 82–126 region) if these data are not available.

Systematic calculations of low-lying states of even-even nuclei within the nucleon pair approximation

The magnetic moments of ( $\mathrm{double}\mathrm{magic}+1\mathrm{proton}$) nuclei having a ``jack-knife'' $j\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}l\ensuremath{-}s$ configuration form crucial tests for the theoretical treatment of mesonic exchange currents and core polarization effects in finite nuclei. The reported precision measurement and analysis of the magnetic moment of ${}^{133}\mathrm{Sb}$ ( ${}^{132}\mathrm{Sn}+\mathrm{one}{g}_{7/2}\mathrm{proton}$) $\ensuremath{\mu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.00(1){\ensuremath{\mu}}_{N}$ provides the first such test in medium-heavy nuclei. In addition, new data on the N dependence of the ${7/2}^{+}{}^{123\ensuremath{-}133}\mathrm{Sb}$ ground state moments are presented. Analysis in terms of particle-core coupling indicates slightly negative collective g factors of heavy Sn core nuclei.

Magnetic Moments of Odd- A Sb Isotopes to 133 Sb: Significant Evidence for Mesonic Exchange Current Contributions and on Core Collective g Factors

A series of low temperature nuclear orientation (LTNO) experiments has been initiated to measure accurately ground-state magnetic dipole moments of a sequence of odd-proton antimony isotopes up to the neutron shell closure at N=82 using the sensitive technique of nuclear magnetic resonance on oriented nuclei (NMR/ON). The main aim of this investigation is to clarify the single-particle+collective core coupling mechanism in the heavy antimony isotopes and its influence on the value of magnetic dipole moment. This paper reports results of precision measurement of the magnetic dipole moments of $^{127}\mathrm{Sb}$ and $^{129}\mathrm{Sb}$. \textcopyright{} 1996 The American Physical Society.

D. Doran

Papers

Magnetic Moments of Odd- A Sb Isotopes to 133 Sb: Significant Evidence for Mesonic Exchange Current Contributions and on Core Collective g Factors

Magnetic dipole moment of 127Sb and 129Sb by nuclear magnetic resonance on oriented nuclei.

Low-temperature nuclear orientation on the Kondo system CexNd1-xNi.