Collectivity and configuration mixing in 186,188Pb and 194Po

Lifetimes of prolate intruder states in 186Pb and oblate intruder states in 194Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in 188Pb up to the 8+ state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters |β2|=0.29(5) and |β2|=0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes

Lifetimes of intruder states in 186 Pb, 188 Pb and 194 Po

Lifetimes of prolate intruder states in 186Pb and 188Pb and oblate intruder states in 194Po have been determined through recoil distance Doppler-shift lifetime measurements. Deformation parameters of | β2 | = 0.29 (5) and | β2 | = 0.17(3) have been ext

Isomer Studies for Nuclei near the Proton Drip Line in the Mass 130-160 Region

This report details the status of an experimental research programme which has studied isomeric states in the mass 130-160 region of the nuclear chart. Several new isomers have been established and characterised near the proton drip Une using a recoil isomer tagging technique at the University of Jyväskylä, Finland. The latest experiments have been performed with a modified setup where the standard GREAT focal-plane double-sided silicon-strip detector was changed to a dual multi-wire proportional-counter arrangement. This new setup has improved capability for short-lived isomer studies where high focal-plane rates can be tolerated. The results of key recent experiments for nuclei situated above (153Yb,152Tm) and below (136Pm,142Tb) the N=82 shell gap were presented along with an interpretation for the isomers. Finally, the future prospects of the technique, using an isomer-tagged differential-plunger setup, were discussed. This technique will be capable of establishing the deformation of the states above the isomers and will aid in the process of assigning underlying single-particle configurations to the isomeric states

Investigation of nuclear collectivity in the neutron mid-shell nucleus 186 Pb

For the first time, non-yrast structures of the neutron mid-shell nucleus Pb186 have been identified in an in-beam I -ray spectroscopy measurement using the recoil-decay tagging technique. The yrast band has been tentatively extended up to IÏ€=20+, re

Evidence for oblate structure in Pb-186

In-beam 3 coincidence data have been collected for Pb186 by combining the JUROGAM Ge-detector array and the GREAT spectrometer with the RITU gas-filled recoil separator for recoil-decay tagging measurements. In addition to the known prolate yrast band i

α\alpha decay of 159^{159}Re and proton emission from 155^{155}Ta

The alpha decay of Re-159 has been observed for the first time in reactions of 300 MeV Ni-58 ions with an isotopically enriched Cd-106 target. The Re-159 ions were separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The alpha decay emanates from the proton-emitting pi h(11/2) state in Re-159 with an energy of E-alpha=6776 +/- 26 keV and a branching ratio of 7.5 +/- 3.5%. This alpha decay populates a state in the closed neutron shell nucleus Ta-155, which decays by emitting 1444 +/- 15 keV protons with a half-life of 2.9(-1.1)(+1.5) ms. These values are consistent with the emission of the proton from a pi h(11/2) orbital. These results fit in with the systematics of proton and alpha-particle separation energies in the region, but disagree with the previously reported decay properties of Ta-15

Yrast states and band crossings in the neutron-deficient platinum isotopes 169-173 Pt

The yrast states in the light platinum isotopes Pt169-173 have been investigated in a recoil-decay tagging experiment using the JUROGAM γ-ray spectrometer in conjunction with the RITU gas-filled recoil separator and the GREAT tagging spectrometer. Gamma

Collectivity in neutron-deficient Pb and Po nuclei

Lifetimes of low-lying yrast states in186Pb and194Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in188Pb up to the 8+ state were carried out using the recoil gating method. The deformation parameters β2 = 0.29(5) and β2 for the prolate (186,188Pb) and the oblate (194Po) bands, respectively, have been extracted from the measured lifetimes

Recoil-fission tagging of the transfermium nucleus 252 No

An in-beam study of the transfermium nucleus 252No has been performed using the JUROSPHERE II array of germanium detectors coupled to the gas-filled recoil separator RITU. A new technique of recoil-fission tagging was used to extract tagged γ-ray data.

In-beam gamma ray and conversion electron study of 250 Fm

We report on a set of in-beam studies of excited states in Fm250. We detected prompt γ rays by using the JUROSPHERE IV array and conversion electrons by using the SACRED spectrometer. Both devices were used in conjunction with the RITU gas-filled recoi