0000000000877903
AUTHOR
V. Koponen
Submillisecond On-Line Mass Separation of Nonvolatile Radioactive Elements: An Application of Charge Exchange and Thermalization Processes of Primary Recoil Ions in Helium
Transportation of thermalized primary recoil ions from nuclear reactions by helium flow has been investigated as a means of injecting short-lived radioactive nuclides into an on-line isotope separator. Several short-lived radioactive isotopes of highly nonvolatile elements such as B, Sc, Nb, and W have been separated. The efficiency for heavy nuclides with half-lives above 1 ms is between 1 and 10%. The shortest-lived activity identified in an on-line separation is the 182-\ensuremath{\mu}s isomeric state in $^{207}\mathrm{Bi}$.
Half-life and configuration of the 1/2+ intruder state in203Bi
The decay properties of theJπ=1/2+,Eexc=1,098 keV state in203Bi were studied. The state was populated via the204Pb(p, 2n) reaction and the activity was studied with the ion guide isotope separator on-line system IGISOL. The half-life of the 1/2+ state was measured to beT1/2=303 ±5 ms. From this value the partial half-lives of the three depopulating branches 1/2+ →7/2− (E3), 1/2+→5/2− (E3 +M2) and 1/2+→9/2 g.s. − (M4) were deduced. Since all the transitions are configuration forbidden in first order, a detailed study of second-order shell-model configuration mixing could be performed.
Half-life measurements for neutron-rich Tc, Ru, Rh, and Pd isotopes. Identification of the new isotopesTc111,Ru113, andRh113
The decays of three new neutron-rich nuclides $^{111}\mathrm{Tc}$, $^{113}\mathrm{Ru}$, and $^{113}\mathrm{Rh}$ have been observed at an on-line isotope separator facility. In addition, the beta decays of several other n-rich isotopes with Ag100 have been studied for the first time. The new half-lives reported in this work include: $^{111}\mathrm{Tc}$ [${T}_{1/2}$=0.30(3) s], $^{111}\mathrm{Ru}$ [2.12(7) s], $^{112}\mathrm{Ru}$ [1.75(7) s], $^{113}\mathrm{Ru}$ [0.80(10) s], $^{113}\mathrm{Rh}$ [2.72(22) s], and $^{118}\mathrm{Pd}$ [2.24(17) s]. In general, these results support the microscopic theoretical half-life predictions below Z=50.
Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium
Neutron-rich isotopes of palladium were produced via the fission of238U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyvaskyla. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For114Pd and116Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of118Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT1/2=1.9±0.1 s andQβ=4.…
Gamow-Teller Beta Decay of Neutron Rich Tc, Ru, Rh and Pd Isotopes
During recent experiments at the IGISOL-facility several new neutron rich nuclides have been discovered, including the first direct observations of the beta decays of 111Tc, 112Ru, 113Ru, 114Ru, 113Rh, 115Rh, 116Rh and 118Pd. The role of the νg7/2 → πg9/2 transformation in the beta decays of the odd-odd 110–116Rh and the even-even 114–118Pd isotopes is shown to be dominant. The experimental results are compared with shell model calculations including deformation and pairing.