J. P. Omtvedt

Gamma-ray and delayed neutron branching data for the new or little known isotopes84,85Ge and84,85As

The branchings (absolute intensities) of γ-rays following the decay of84,85Ge and84,85As have been determined using mass-separated samples. Our results include the first identification of85Ge and the first γ-ray data for84Ge. Values of the delayed neutron emission probabilities, Pn, of84Ge and85As were also deduced from the data, together with a lower limit of this quantity for85Ge. The deduced Pn of about 39 % for the important neutron emitter85As is substantially larger than the values of about 22–23 % obtained in previous indirect determinations.

The doubly closed shell nucleus 132Sn: Collectivity and p-h states

The angular momenta and parities of the low lying states of 132Sn have been firmly determined through studies of the β-decay of 132In. The lowest lying state with a negative parity is shown to have a collective octupole character. Several particle-hole multiplets have been identified, including the lowest lying proton excitation. Theoretical estimates of multiplet positions and multiplet splittings, based on the analogy with 208Pb, agree well with the data. More than about 20% of the theoretically estimated bound states of 132Sn have been identified.

Study of theβ+/EC decay of the neutron deficient nuclei76,78Sr and79Y

The β+/EC decay of the neutron deficient nuclei76,78Sr and79Y was studied employing mass separated molecular beams of SrF+ and YF2+ from the ISOLDE mass separator. The halflives of76,78Sr and79Y were measured as t1/2=8.9(3)s, 159(8)s and 14.4(15)s, respectively, and decay schemes were established for76Sr and79Y. In the78Sr decay 10 new γ-ray transitions were identified.

The decay of84As

The decay properties of84As have been investigated with mass separated sources. Only one β-decaying state is seen, contradictory to previous observations. The halflife is found to be 4.5±0.2 s. A detailed decay scheme has been constructed, and 33 excited states in84Se have been determined.

New high spin isomers obtained in thermal fission

The product nuclei following fission often are initially highly excited and have high angular momenta. As a consequence, there is a substantial probability for the population of isomeric yrast traps in the vicinity of closed shells. The excitation energies and decay properties of such isomers give important formation regarding the shell structure and interaction energies. Recent experiments at the OSIRIS mass separator have revealed a number of isomers in the 132Sn region having angular momenta exceeding 10 units. A brief presentation is given of some experimental results and their interpretation.

Detailed spectroscopy of doubly-magic 132Sn and its neighbours; Perspective for further studies at PIAFE

Abstract Experimental studies at the OSIRIS fission-product mass separator have yielded a wealth of new results on the doubly-magic region near 132 Sn. In the following we focus on two aspects of the new results: on the evidence for octupole collectivity of the 3 1 − state in 132 Sn and on the similarity of the 208 Pb and 132 Sn regions as evidenced from the modelling of the low excitations in 132 Sb. The Stage-I of the PIAFE facility recently proposed at Grenoble will offer exciting possibilities for even more detailed studies of the doubly magic regions near 132 Sn and 78 Ni (the latter for the first time).

Identification of Reaction Products in 50Ti+249Cf Reactions at TASCA

The neutron-rich nuclei 33P and 33S in the upper sd-shell were investigated by means of the 26Mg(13C,npa) and 26Mg(13C,2na) fusion-evaporation reactions. Excited states with intermediate and high spins have been populated. The level schemes of both nuclei have been considerably extended. Utilizing the gammagamma-angular correlation method the spin-parity assignment of the new excited states in 33P has been investigated. The experimentally determined energy levels as well as the known reduced transition probabilities (i.e. B(M1) and B(E2) values) from both nuclei were compared to 0hbaromega and 1hbaromega truncated p-sd-pf shell-model calculations using the PSDPF interaction. For the energy levels a very good agreement between experiment and theory was shown for both 33P and 33S. However, for B(M1) and B(E2) values the calculated values cannot reproduce the experimental results with satisfying agreement for all transitions. In some places the discrepancy between experiment and theory is even large, which requires further experimental as well as theoretical investigation of this thesis for these nuclei. The second part was focused on the upgrade and commissioning tests of the Lund- York-Cologne CAlorimeter (LYCCA). As a key device of the High resolution In-flight SPECtroscopy (HISPEC) campaign of the FAIR/NUSTAR collaboration, LYCCA was designed to identify the reaction products after the secondary target, as well as to track the particle trajectory event by event. After the successful employment of the precursor LYCCA-0 in the PreSPEC campaign, the electronic as well as mechanic components of the LYCCA system were upgraded by STFC Daresbury Laboratory. Using the high integrated AIDA Front-End electronics with ASICs the signals from more than thousand DSSSD-channels were pre-amplified and processed. Since 2016, the new LYCCA setup is located at the Cologne tandem accelerator. Triple-Alpha tests and in-beam experiments of elastic scattering were carried out to check the specifications of the system after the upgrade. The obtained results allow first important conclusions about energy resolution and efficiency of the calorimeter at low energies for future NUSTAR experiments.Di Nitto, A.; Khuyagbaatar, J.; Ackermann, D.; Adamczewski-Musch, J.; Andersson, LiseLotte; Badura, E.; Block, M; Brand, H.; Cox, D. M.; Düllmann, Ch. E.; Dvorak, J.; Eberhardt, K.; Ellison, P. A.; Esker, N. E.; Even, J.; Fahlander, Claes; Forsberg, Ulrika; Gates, J.M.; Golubev, Pavel; Gothe, O.; Gregorich, K.E.; Hartmann, W.; Herzberg, R.-D.; Heßberger, F. P.; Hoffmann, J.; Hollinger, R.; Hübner, A.; Jäger, E.; Jeppsson, J.; Kindler, B.; Klein, S.; Kojouharov, I.; Kratz, J.V.; Krier, J.; Kurz, N.; Lahiri, S.; Linev, S.; Lommel, B.; Maiti, M.; Mändl, R.; Merchán, E.; Minami, S.; Mistry, A. K.; Mokry, Ch.; Nitsche, H.; Omtvedt, J. P.; Pang, G.; Pysmenetska, I.; Renisch, D.; Rudolph, Dirk

Recoil-alpha-fission and Recoil-alpha-alpha-fission Chains Stemming from Element 115

Rudolph, Dirk; Forsberg, Ulrika; Düllmann, C. E.; Golubev, Pavel; Heßberger, F.P.; Khuyagbaatar, J.; Kratz, J. V.; Sarmiento, Luis; Yakushev, A.; Ackermann, D.; Andersson, L.; Block, M.; Brand, H.; Cox, D.; Derkx, X.; Di Nitto, A.; Eberhardt, K.; Even, J.; Fahlander, Claes; Gates, J. M.; Gerl, J.; Gregorich, E. K.; Gross, C. J.; Herzberg, R.-D.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Runke, J.; Rykaczewski, K.; Schädel, M.; Schaffner, H.; Schausten, B.; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Wiehl, N. Published in: GSI Report

Chemical Study of Fl, Cn, their Lighter Homologs and Rn at TASCA

Yakushev, A.; Lens, L.; Dullmann, C. E.; Ackermann, D.; Asai, M.; Ballof, J.; Block, M.; Brand, H.; Cox, D. M.; Despotopulos, J.; Di Nitto, A.; Eberhardt, K.; Even, J.; Fan, F.; Golubev, Pavel; Haba, H.; Hartmann, W.; Herzberg, R.-D.; Hesberger, F.P.; Hoffmann, J.; Hubner, A.; Jager, E.; Khuyagbaatar, J.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Lahiri, S.; Lommel, B.; Maiti, M.; Mistry, A.; Mokry, C.; Moody, K.; Nagame, Y.; Omtvedt, J. P.; Papadakis, P.; Qin, Z.; Rudolph, Dirk; Runke, J.; Rusanov, I.; Sarmiento, Luis; Sato, T.; Schadel, M.; Scharrer, P.; Schausten, B.; Shaughnessy, D.; Steiner, J.; Thorle-Pospiech, P.; Trautmann, N.; Uusitalo, J.

Element 115 Studied with TASISpec

D. Rudolph1, U. Forsberg1, P. Golubev1, L.G. Sarmiento1, A. Yakushev2, L.-L. Andersson3, A. Di Nitto4, Ch.E. Dullmann2,3,4, J.M. Gates5, K.E. Gregorich5, C.J. Gross6, R.-D. Herzberg7, F.P. Hesberger2,3, J. Khuyagbaatar3, J.V. Kratz4, K. Rykaczewski6, M. Schadel2,8, S. ◦ Aberg1, D. Ackermann2, M. Block2, H. Brand2, B.G. Carlsson1, D. Cox7, X. Derkx3,4, K. Eberhardt3,4, J. Even3, C. Fahlander1, J. Gerl2, E. Jager2, B. Kindler2, J. Krier2, I. Kojouharov2, N. Kurz2, B. Lommel2, A. Mistry7, C. Mokry3,4, H. Nitsche5, J.P. Omtvedt9, P. Papadakis7, I. Ragnarsson1, J. Runke2, H. Schaffner2, B. Schausten2, P. Thorle-Pospiech3,4, T. Torres2, T. Traut4, N. Trautmann4, A. Turler10, A. Ward7, D.E. Ward1, and N. Wiehl3,4 1Lund University, Lund, Sweden; 2GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt, Germany; 3Helmholtz Institute Mainz, Mainz, Germany; 4Johannes Gutenberg-Universitat Mainz, Mainz, Germany; 5Lawrence Berkeley National Laboratory, Berkeley, USA; 6Oak Ridge National Laboratory, Oak Ridge, USA; 7University of Liverpool, Liverpool, United Kingdom; 8Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan; 9University of Oslo, Oslo, Norway; 10Paul Scherrer Institute and University of Bern, Villigen, Switzerland