Proton-neutron pairing correlations in the self-conjugate nucleus 42Sc

Á Koszorús,L.J Vormawah,R Beerwerth,M.L Bissell,P Campbell,B Cheal,C.S Devlin,T Eronen,S Fritzsche,S Geldhof,H Heylen,J.D Holt,A Jokinen,S Kelly,I.D Moore,T Miyagi,S Rinta-Antila,A Voss,C Wraith

doi:10.1016/j.physletb.2021.136439

Á Koszorús, L.J Vormawah + Show 17 more

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https://doi.org/10.1016/j.physletb.2021.136439

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Collinear laser spectroscopy of the N=Z=21 self-conjugate nucleus 42Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the Iπ=0+ ground state and the Iπ=7+ isomer via the measurement of the 42g,42mSc isomer shift. New multi-configurational Dirac-Fock calculations for the atomic mass shift and field shift factors have enabled a recalibration of the charge radii of the 42−46Sc isotopes which were measured previously. While consistent with the treatment of proton-neutron, proton-proton and neutron-neutron pairing on an equal footing, the reduction in size for the isomer is observed to be of a significantly larger magnitude than that expected from both shell-model and ab-initio calculations. The measured nuclear magnetic dipole moment and electric quadruple moment, on the other hand, are in good agreement with simple empirical estimates and shell-model calculations.

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Collinear laser spectroscopy of the N = Z = 21 self-conjugate nucleus 42Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the Iπ = 0+ ground state and the Iπ = 7+ isomer via the measurement of the 42g,42mSc isomer shift
The results which we report here, together with those of the previous study [4], are qualitatively consistent with the intuitive picture of π ν pairing correlations along the line of N = Z
The negative value obtained for δ r2 42g,42m indicates a larger charge radius for the 0+ ground state than for the 7+ isomer, as expected from employing an orbital blocking picture

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A study of pairing effects on the relative mean-square charge radii of multi-quasiparticle isomers [3], such as 97m2Y, 176mYb and 178m1Hf, was motivated by the measurement of 178m2Hf by Boos et al [5] All of these isomers were found to have a smaller meansquare charge radius than their respective ground states irrespective of nuclear deformation. This offered an explanation into the observed odd-even staggering of nuclear charge radii [6] as arising from a combination of increasing rigidity (i.e. a reduction in the root mean square quadrupole deformation value towards the mean value) or decreasing surface diffuseness, due to the orbital (Pauli) blocking of the odd nucleon [3].

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