Characterization of octupole-type structures in Th-221

International audienceA detailed level scheme for Th-221 has been established in an experiment using the O-18 + Pb-207 reaction at 96 MeV. The evaporation residues from this fissile system were selected with the HERCULES detector array and residue-gated gamma rays were measured with Gammasphere. Three band structures of interlinked, alternating-parity levels are observed, two of which are non-yrast. In addition, several high-lying excitations are found. The yrast band is seen up to spin-parity 37/2(-) and 39/2(+), beyond which a high-spin feeding transition is observed. The non-yrast sequences are interpreted as parity-doublet structures, based on a configuration similar to that of the yrast band in Th-223 (K = 5/2). The key properties of even-odd nuclei in this mass region [B(E1)/B(E2) and B(M1)/B(E2) ratios, spin alignments, parity splittings] are reviewed

Isomer and decay studies for the rp process at IGISOL

This article reviews the decay studies of neutron-deficient nuclei within the mass region \ensuremath A=56\mbox{--}100 performed at the Ion-Guide Isotope Separator On-Line (IGISOL) facility in the University of Jyväskylä over last 25 years. Development from He-jet measurements to on-line mass spectrometry, and eventually to atomic mass measurements and post-trap spectroscopy at IGISOL, has yielded studies of around 100 neutron-deficient nuclei over the years. The studies form a solid foundation to astrophysical rp -process path modelling. The focus is on isomers studied either via spectroscopy or via Penning-trap mass measurements. The review is complemented with recent results on the ground and isomeric states of 90Tc . The excitation energy of the low-spin isomer in 90Tc has been measured as \ensuremath E_x=144.1(17) keV with JYFLTRAP double Penning trap and the ground state of 90Tc has been confirmed to be the (8+) state with a half-life of \ensuremath T_{1/2}=49.2(4) s. Finally, the mass-excess results for the spin-gap isomers 53Co m and 95Pd m and implications from the JYFLTRAP mass measurements for the (21+) isomer in 94Ag are discussed