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

Collinear laser spectroscopy of the $N=Z=21$ self-conjugate nucleus $^{42}$Sc has been performed at JYFL IGISOL IV facility in order to determine change nuclear mean-square charge radius between $I^{\pi}=0^{+}$ ground state and $I^{\pi}=7^{+}$ isomer via measurement $^{42\mathrm{g},42\mathrm{m}}$Sc shift. New multi-configurational Dirac-Fock calculations for atomic mass shift field factors have enabled a recalibration radii $^{42-46}$Sc isotopes which were measured previously. While consistent with treatment proton-neutron, proton-proton neutron-neutron pairing on an equal footing, reduction size is observed be significantly larger magnitude than that expected from both shell model ab-initio calculations.