Universal Effective Charges in the sd and fp Shells

The 247-keV state in ^{54}Sc, populated in the β decay of ^{54}Ca, is reported here as a nanosecond isomer with a half-life of 26.0(22) ns. The state is interpreted as the 1^{+} member of the πf_{7/2}⊗νf_{5/2} spin-coupled multiplet, which decays to the 3^{+},πf_{7/2}⊗νp_{1/2} ground state. The new half-life corresponds to a pure E2 transition with a strength of 1.93(16) W.u., providing the most precise, unambiguous B(E2) value in the neutron-rich fp region to date for a nucleus with valence protons above Z=20. Notably, it is roughly 4 times larger than the B(E2;1/2^{-}→5/2^{-}) value in ^{55}Ca. The results, as compared to semiempirical and ab initio shell-model calculations, indicate (1) a weak N=34 subshell gap relative to N=32, (2) a large E2 enhancement in Sc as compared to Ca due to 1p-1h proton excitations across Z=28, and (3) empirical effective proton and neutron charges e_{π}=1.30(8)e and e_{ν}=0.452(7)e, respectively, that are in contrast to reports of e_{π}≈1.1-1.15e and e_{ν}≈0.6-0.8e for fp-shell nuclei near N=Z. We demonstrate that these reports are erroneous and that, in fact, a universal set of effective charges can be used across the sd and fp shells.