L. Spanier

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.

Experimental masses at doubly magic nuclide 132Sn

The beta-decay energies have been measured for nuclides very far off the beta-stability line and close to double-magic 132Sn. The experiments have been performed at the improved OSIRIS-facility by using a Ge(HP)-detector. The mass values for fifteen nuclides of In, Sn, Sb and Te with mass numbers from the region of A = (132 ± 0, 1, 2) have been determined. The accuracy of the obtained data considerably exceeds the known one from literature. The proton-neutron effective interaction energies derived from mass values for the tin region are equal or very close to the ones for the lead region, if (l, j) and (l + 1, j + 1)-configurations for both protons and neutrons are compared. This result supports the idea of a universal shell model discription of different magic regions of heavy nuclides, which may allow to predict properties of yet unknown magic nuclides throughout the nuclidic chart.

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.

Some studies of molecular ions obtained from a U + C target at > 2100°C

Abstract The OSIRIS ISOL-facility at Studsvik is used for studies of short lived products from reactor neutron induced fission. Several species of molecular ions are produced in the target, forming sidebands to the fission mass distribution. Other species are obtained when reactive gases are introduced into the target chamber. Observations of the temperature stability of molecular ions and their formation probabilities under different conditions are reported.