β - and γ -spectroscopy study of Pd119 and Ag

Abstract

Neutron-rich 119 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 119 Pd. Their β − decay was measured with γ γ -and βγ -spectroscopy methods using low-energy germanium detectors and a thin plastic scintillator. Two distinct nuclear-level structures were observed in 119 Ag, based on the 1/2 − and 7/2 + isomers reported previously. The β − -decay work was complemented by a prompt-γ study of levels in 119 Ag populated in spontaneous fission of 252 Cf, performed using the Gammasphere array of germanium detectors. Contrary to previous suggestions, our data show that the 1/2 − isomer is located below the 7/2 + isomer and is proposed as a new ground state of 119 Ag with the 7/2 + isomer excitation energy determined to be 33.4 keV. Our data indicate that there are two β unstable isomers in 119 Pd, a proposed ground state of 119 Pd with tentative spin 1/2 + or 3/2 + and a half-life of 0.88 s and the other one about 350 keV above, having spin (11/2 − ) and a half-life of 0.85 s. The higher-energy isomer probably decays to the 1/2 + or 3/2 + ground state via a γ cascade comprising 18.7-219.8-X-keV transitions. The unobserved isomeric transition with energy X ≈ 100 keV probably has an E 3 multipolarity. Its hindrance factor is significantly lower than for analogous E 3 isomeric transitions in lighter Pd isotopes, suggesting an oblate deformation of levels in 119 Pd. Oblate configurations in 119 Ag are discussed also.

Simultaneous description of β decay and low-lying structure of neutron-rich even- and odd-mass Rh and Pd nuclei

“…The experimental data included in panel (c) are taken from Ref [71]. for 117 Pd, from Ref [72]. for119 Pd, and from the NNDC database [70] for the other nuclei.…”