J. Perkowski

In-beam and decay spectroscopy of very neutron deficient iridium nuclei

Iridium nuclei at and beyond the proton drip line have been studied via fusion evaporation reactions. A reaction of 92Mo(78Kr, p2n) at a beam energy of 360 MeV and target thickness 500 µg cm−2 was employed to study 167,167mIr. A reaction of 112Sn(58Ni, p2n) at a beam energy of 266 MeV and target thickness 500 µg cm−2 was used to study 169,169mIr. The experiments were performed at the University of Jyvaskyla utilizing the RITU separator in conjunction with the focal plane GREAT spectrometer and the JUROGAM Ge array at the target position. Excited states feeding both the ground state and isomeric state in 169Ir, excited states feeding the ground state of 167Ir and the ground state alpha decay of 165Re have been observed for the first time along with excited states feeding 167mIr. Experimental spectroscopic factors and reduced widths have been obtained for the proton and alpha decay of these nuclei.

First identification of excited states in 169Ir

Gamma rays populating the alpha-decaying isomeric state in Ir-169 have been observed for the first time. The experiment employed the recoil-decay tagging method using the JUROGAM gamma-ray spectrom ...

Yrast structures in the light Pt isotopes 169?173Pt

The exploitation of the recoil-decay tagging (RDT) technique has reinvigorated experimental investigations of the shape coexistence phenomenon in heavy neutron-deficient nuclei. In a recent experiment using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator, excited states have been investigated in the light platinum isotopes. In addition to extending the yrast sequences in 170Pt and 172Pt, the first observation of excited states in the odd-N isotopes, 169Pt and 173Pt, is reported. The bands are discussed in terms of trends in level excitation energies as a function of neutron number.

The influence of quasineutron configurations on 161Ta and nearby odd‐A nuclei

Several strongly coupled bands in the neutron‐deficient nucleus 161Ta have been identified and quasiparticle configuration assignments have been made on the basis of rotational alignments and cranked shell model calculations. The level scheme elucidated for 161Ta highlights the competition between the ν(h9/2) and ν(i13/2) orbitals to form the yrast spectrum. The band structures in 161Ta also provide new insights into the structural features of other heavy odd‐A nuclei populated with much lower reaction cross sections in this region at the proton drip line.

Spectroscopy of odd‐proton nuclei in the region of 254No

Two rotational bands have been found in the transfermium nuclei 251Md and 255Lr, the latter being the heaviest nucleus so far studied in‐beam. Both are assigned to a [521]1/2− Nilsson state by comparison to theory. The experiments have been carried out in the Accelerator Laboratory of the University of Jyvaskyla (JYFL), where the array of germanium detectors JUROGAM was used in conjunction with the recoil‐seperator RITU and the focal‐plane setup GREAT for gamma‐spectroscopic studies.

Evidence for a strongly‐coupled band in very neutron‐deficient odd‐mass nucleus 185Pb

For the first time, excitated states in very neutron‐deficient odd‐mass nucleus 185Pb have been observed in an in‐beam γ‐ray measurement. The present data provide evidence for a strong‐coupling of an odd‐neutron hole to the even‐mass prolate core in the light Pb isotopes.

In‐beam spectroscopy of 254No

Evidence for the presence of non‐yrast states in 254No has been observed in two different in‐beam experiments carried out at the University of Jyvaskyla. Firstly an in‐beam conversion electron spectroscopic study was performed with the SACRED spectrometer, revealing a distribution consisting of high‐multiplicity electron cascades. This provides an indirect proof of the presence of high K‐bands in 254No. In a more recent in‐beam γ‐ray spectroscopic measurement, evidence for the decay of non‐yrast states in 254No has been observed for the first time. It is speculated that the observation of high‐energy γ rays is due to the decay of a K = 3 band‐head state.