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

Collinear laser spectroscopy is performed on the nickel isotopes <math display="inline"><mrow><mmultiscripts><mrow><mi>Ni</mi></mrow><mprescripts/><none/><mrow><mn>58</mn><mo>-</mo><mn>68</mn><mo>,</mo><mn>70</mn></mrow></mmultiscripts></mrow></math>, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii <math display="inline"><msub><mi>R</mi><mi>c</mi></msub></math> are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction <math display="inline"><msub><mrow><mi>NNLO</mi></mrow><mrow><mi>sat</mi></mrow></msub></math>, which allows an assessment of their accuracy. We find agreement with experiment in differential radii <math display="inline"><mrow><mi>δ</mi><mrow><mo stretchy="false">⟨</mo><msubsup><mrow><mi>r</mi></mrow><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msubsup><mo stretchy="false">⟩</mo></mrow></mrow></math> for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for <math display="inline"><msub><mrow><mi>NNLO</mi></mrow><mrow><mi>sat</mi></mrow></msub></math>. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional <math display="inline"><mrow><mi>Fy</mi><mo stretchy="false">(</mo><mi mathvariant="normal">Δ</mi><mi>r</mi><mo>,</mo><mi>HFB</mi><mo stretchy="false">)</mo></mrow></math>.