D. Jerrestam

Efficiency and delay of the integrated target-ion source of OSIRIS

Abstract The new compact target and ion source system of the OSIRIS ISOL-facility at Studsvik has now been in use for about five years. The system is used for studies of short lived nuclei obtained through fission with reactor neutrons. The ion source can simply be switched between two modes of operation, one being (thermal) surface ionization and the other an electron impact induced plasma mode. The efficiency for most elements in the fission product region has been measured. The use of a substantial (gram quantity) amount of target material introduces a delay between a fission event and the subsequent ionization of the products. This delay in a U+C target has been analyzed for several elements. Some observations of nuclidic yields as a function of the target temperature are reported.

Rotational bands in 107Cd

Abstract High-spin states in 107Cd were populated by the reaction 94Zr(17O, 4n) at 80 MeV and their decay was studied by γ-spectroscopic methods using the NORDBALL multi-detector array. The experiment included γ-ray yields, γ-coincidences and γ-ray angular correlation measurements. Rotational bands were observed up to spin 39 2 and ( 51 2 + ) in the negative- and positive-parity bands, respectively. Calculations of total routhian surfaces and quasi-particle routhians have been performed and are used for assigning quasiparticle configurations to the bands. In the g 7 2 neutron band, a h 11 2 neutron alignment is observed. A large signature spliting is expected in the ν g 7 2 band before the band crossing. For the band built on a single ν h 11 2 quasiparticle, an alignment of either g 7 2 or h 11 2 neutrons is proposed. Shape change effects are discussed.

Evidence for shape coexistence from few-quasiparticle excitations in 83Kr

Excited states in 83Kr were studied in the 82Se(α, 3n) reaction using in-beam γ-ray spectroscopy. Measurements of γγ coincidences, excitation functions, angular distributions and linear polarization of the γ-rays were carried out and levels were established up to I = 292. Most of the levels above 2.5 MeV could be grouped into 3 band-like sequences. Lifetimes or limits of lifetimes were determined for 8 members of these bands using the DSA method. The positive-parity 3qp band, I = 212 to 292, indicates a prolate deformation similar to the corresponding band in 81Kr. In contrast, only low collectivity was found for a ΔI = 2 sequence built on the 172− yrast state and reaching up to I = (292). From similarities of the level spacings with the ground state bands and 2qp bands of the even-mass neighbours, the 3qp configuration ν(g92)−2νp12 is proposed for this sequence. Another band, comprising levels with Iπ = 132− to (272−) in a ΔI = 1 sequence, displays a sharp decrease of the intraband M1 transition rates with increasing spin.

High-spin studies of the neutron deficient nuclei In-103, In-105, In-107, and In-109

High-spin states of the isotopes In-103,In-105,In-107,In-109 have been investigated using in-beam gamma-ray spectroscopic methods. Results from three different experiments are presented. Targets of Fe-54, Cr-50, and Mo-92 were bombarded by a 270 and 261 MeV Ni-58 beam and by a 95 MeV F-19 beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1 pi neutron detector system. As a result of these experiments the level schemes of In-103,In-105,In-107,In-109 were significantly extended. Excited states of these odd-A indium isotopes are discussed within the framework of the nuclear shell model and the hole-core coupling scheme. The systematics of excited states of light odd-A indium isotopes is also discussed

Collective excitations in 106Cd

High Spin states in 106Cd were populated by the reactions Zr-94(O-17, 5n) and Ge(S-32, 4n) at 80 MeV and at 148 MeV, respectively. The gamma-decay was studied by gamma-spectroscopic methods using t ...

In-beam gamma-ray spectroscopy of Cd-102

Neutron deficient nuclei close to 100Sn have been studied using the NORDBALL Ge-detector array together with ancillary particle detectors. Evaporation residues from the compound nucleus 108Te were identified with charged particle and neutron detectors. In this paper a considerable extension of the level scheme of the nucleus 102Cd is presented. The strongest cascade of the new level scheme reveals an irregular sequence of dipole transitions above Iπ = 10+ extending up to spin 17. A strongly populated rather regular side band consisting of four quadrupole transitions ranging from spin 9 to spin 17 was also discovered. This band was tentatively assigned negative parity. Shell model calculations were performed and a very good agreement with the experimental results was found. The excited states could successfully be interpreted as neutron particle and proton hole excitations with respect to the doubly closed core 50100Sn50.

Collective bands in 106Ag and 107Ag

Abstract The nuclei 106 Ag and 107 Ag have been studied using 80 MeV 17 O ions impinging on 94 Zr. The γ- rays were detected with the NORDBALL array and light charged particles with a charged-particle detector system. Rotational bands have been established using γ-ray yields, γγ coincidences and angular correlation information. Calculations of spin diabatic surfaces have been done and are used for assigning quasiparticle configurations to the bands. Deformation effects are observed in almost all bands.

A “superdeformed” band in 103Pd

Abstract A superdeformed (SD) band in 103Pd was studied using the reaction 76Ge(34S,α3n) at 148 MeV. Yields of γ-rays, γ-γ coincidences and γ-ray angular correlation measurements were obtained with the NordBall multi-detector system. The SD band is compared with similar bands in 104,105Pd. Calculations of spin diabatic surfaces have been performed and are used for assigning deformation parameters and quasiparticle configurations to the bands. Additional occupation of intruder orbitals from π or ν h 11 2 and the ν i 13 2 [660] 1 2 , in combination with band terminations of the normal deformed bands may explain the existence of the SD band in 103Pd.

Alignments and band termination in99,100Ru

Abstracth11/2 neutron and g9/2 proton alignments in99,100Ru deduced from comparisons of experimental Routhians and aligned angular momenta to cranking model calculations. There is indication of band termination in100Ru.

On the moment of inertia in deformed Ba-Xe nuclei as deduced from gamma-gamma energy correlation experiments

Abstract The γ-rays following reactions induced by bombarding targets of 114, 116, 118, 120, 122 Sn with 118 MeV 12 C ions were investigated using six NaI(Tl) detectors in a two-dimensional coincidence arrangement. Experimental energy-correlation spectra were extracted from the original coincidence matrices. The energy-correlation spectra exhibit the features expected for rotational nuclei and were used to deduce information on the moment of inertia I (2) = ΔI/Δω . The gross properties of the behaviour of I (2) in the Ba-Xe region are discussed together with their interpretation within the cranked shell model (CSM).