27 research outputs found
and -spectroscopy study of Pd and Ag
Neutron-rich Pd nuclei were produced in fission of natural uranium, induced by 25-MeV protons. Fission fragments swiftly extracted with the Ion Guide Isotope Separation On-Line method were mass separated using a dipole magnet and a Penning trap, providing mono-isotopic samples of Pd. Their decay was measured with - and -spectroscopy methods using low-energy germanium detectors and a thin plastic scintillator. Two distinct nuclear-level structures were observed in Ag, based on the and isomers reported previously. The -decay work was complemented by a prompt-γ study of levels in Ag populated in spontaneous fission of Cf, performed using the Gammasphere array of germanium detectors. Contrary to previous suggestions, our data show that the isomer is located below the isomer and is proposed as a new ground state of Ag with the isomer excitation energy determined to be 33.4 keV. Our data indicate that there are two β unstable isomers in Pd, a proposed ground state of Pd with tentative spin or and a half-life of 0.88 s and the other one about 350 keV above, having spin and a half-life of 0.85 s. The higher-energy isomer probably decays to the or ground state via a cascade comprising 18.7-219.8-X-keV transitions. The unobserved isomeric transition with energy X ≈ 100 keV probably has an E3 multipolarity. Its hindrance factor is significantly lower than for analogous E3 isomeric transitions in lighter Pd isotopes, suggesting an oblate deformation of levels in  Pd. Oblate configurations in  Ag are discussed also