0000000000302047
AUTHOR
G. Hagen
Systematics of E2 strength in the sd shell with the valence-space in-medium similarity renormalization group
Background: Recent developments in {\it ab initio} nuclear theory demonstrate promising results in medium- to heavy-mass nuclei. A particular challenge for many of the many-body methodologies, however, is an accurate treatment of the electric-quadrupole, $E2$, strength associated with collectivity. Purpose: The valence-space in-medium similarity renormalization group (VS-IMSRG) is a particularly powerful method for accessing medium- and high-mass nuclei but has been found to underpredict $E2$ strengths. The purpose of this work is to evaluate the isospin dependence of this underprediction. Methods: We perform a systematic comparison of valence-space in-medium similarity renormalization grou…
Charge radius of the short-lived $^{68}$Ni and correlation with the dipole polarizability
We present the first laser spectroscopic measurement of the neutron-rich nucleus $^{68}$Ni at the \mbox{$N=40$} subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability $\alpha_{\rm D}$ has been measured, the combination of these observables provides a benchmark for nuclear structure theory. We compare them to novel coupled-cluster calculations based on different chiral two- and three-nucleon interactions, for which a strong correlation between the charge radius and dipole polarizability is observed, similar to the stable nucleus $^{48}$Ca. Three-particle--three-hole correlations in coupled-cluster theory substant…