β-delayed proton decays and spin assignments for 133Sm and 149Yb
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The proton-rich isotope 133Sm was produced via the fusion evaporation reaction 40Ca + 96Ru. Its β-delayed proton decay was studied by p-γ coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, γ-transitions following the proton emission, as well as β-delayed proton branching ratios to the low-lying states in the grand-daughter nucleus were determined. Comparing the observed β-delayed proton branching ratios with statistical model calculations, the best agreement is found assuming that only one level with the spin of 3/2 in 133Sm decays or two levels with the spins of 1/2 and 5/2 decay with similar half-lives. The configuration-constrained nuclear potential energy surfaces of 133Sm were calculated using the Woods-Saxon-Strutinsky method, which suggests a 1/2- ground state and a 5/2+ isomer with an excitation energy of 120keV. Therefore, the simple (EC+β+) decay scheme of 133Sm in Eur. Phys. J. A 11, 277 (2001) has been revised. In addition, our previous experimental data on the β-delayed proton decay of 149Yb reported in Eur. Phys. J. A 12, 1 (2001) was also analyzed using the same method. The spin-parity of 149Yb is suggested to be 1/2-.
PACS.23.40.Hc Relation with nuclear matrix elements and nuclear structure 21.10.Hw Spin, parity, and isobaric spin 24.10.Pa Thermal and statistical models 27.60.+j 90 ⩽ A ⩽ 149
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