Nuclear Charge Radii of the Nickel Isotopes $^{58-68,70}$Ni

TL;DR

This study measures nuclear charge radii of nickel isotopes using laser spectroscopy and compares the results with various ab initio and density functional theory models, assessing their accuracy.

Contribution

It provides experimental charge radii for nickel isotopes and evaluates the performance of different theoretical approaches against these measurements.

Findings

Agreement in differential radii across all ab initio methods.

Absolute radii match data only with NNLO_sat interaction.

Skyrme functional SV-min aligns more closely with experimental data than Fayans functional.

Abstract

Collinear laser spectroscopy is performed on the nickel isotopes $^{58-68,70}$Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii $R_c$ are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLO$_{\rm sat}$, which allows an assessment of their accuracy. We find agreement with experiment in differential radii $\delta \left\langle r_\mathrm{c}^2 \right\rangle$ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLO$_{\rm sat}$. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy($\Delta r$,HFB).