Charge Radius of the Short-Lived ^{68}Ni and Correlation with the Dipole Polarizability.

S Kaufmann,A Kanellakopoulos,C Wraith,L Wehner,H Heylen,S Sailer,J Simonis,S Malbrunot-Ettenauer,C Gorges,J Billowes,W Gins,G Hagen,A Schwenk,R F García Ruíz ,Tim Ratajczyk ,L V Rodríguez ,B Cheal,R Neugart,Mirko Miorelli ,Liang Xie ,Klaus Blaum ,Z Y Xu ,Sonia Bacca ,M L Bissell ,R Sánchez,G Neyens,X F Yang ,W Nörtershäuser,Deyan T Yordanov

doi:10.1103/physrevlett.124.132502

Abstract

We present the first laser spectroscopic measurement of the neutron-rich nucleus ^{68}Ni at the N=40 subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability α_{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 substantially improve the description of the experimental data, which allows to constrain the neutron radius and neutron skin of ^{68}Ni.

Highlights

Mostly energy density functional (EDF) were used to extract the neutron skin from the dipole polarizability, but in the case of 48Ca the neutron skin was predicted from first principles coupled-cluster calculations to be surprisingly small, only 0.12–0.15 fm [8]. These ab initio calculations starting from two- and three-nucleon interactions based on chiral effective field theory (EFT) [9,10,11] further revealed a correlation between the charge radius and the dipole polarizability, which was predicted to be in the range 2.19–2.60 fm3
In this Letter, we focus on the charge radius of 68Ni, determined by collinear laser spectroscopy
We report on the first coupled-cluster calculation including triples of Rc and αD of 68Ni based on chiral EFT interactions, being the heaviest system for which this has been achieved

Summary

Introduction

These ab initio calculations starting from two- and three-nucleon interactions based on chiral effective field theory (EFT) [9,10,11] further revealed a correlation between the charge radius and the dipole polarizability, which was predicted to be in the range 2.19–2.60 fm3.

Results

Conclusion