Isospin-Forbidden Proton Partial Width inSc41and SimilarA=4n+1Nuclei

Abstract

The lowest $T=\frac{3}{2}$ level in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Sc}$ is observed as an isospin-forbidden resonance in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(p, p_0){}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at $E_{p,\mathrm{lab}}=4.978\mathrm{}$ MeV with proton partial width ${\Gamma }_p=55\mathrm{}\pm 5$ eV, which is about 50 times smaller than that previously assigned and 6 times smaller than theoretical width estimates. The trend of the proton reduced widths for $T=\frac{3}{2}$ isospin-forbidden resonances obtained from ${\Gamma }_p$ values for target nuclei with $4<~Z<~20$ is shown to be consistent with a $Z^2$ dependence.