| 1. |
- Aksyutina, Yu, et al.
(författare)
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Lithium isotopes beyond the drip line
- 2008
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 666:5, s. 430-434
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Tidskriftsartikel (refereegranskat)abstract
- The unbound isotopes 10Li, 12Li and 13Li have been observed after nucleon-knockout reactions at relativistic energies with 11Li and 14Be beams impinging on a liquid hydrogen target. The channels , and were analysed in the ALADIN-LAND setup at GSI. The 10Li data confirm earlier findings, while the 12Li and 13Li nuclei were observed for the first time. The relative-energy spectrum shows that the ground state of 12Li can be described as a virtual s-state with a scattering length of -13.7(1.6) fm. A broad energy spectrum was found for the channel. Based on the assumption that the relative-energy spectrum is dominated by a correlated background presumably stemming from initial correlations in the 14Be ground-state, evidence for a 13Li resonance at 1.47(31) MeV above the threshold with a width around 2 MeV has been found.
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| 2. |
- Aksyutina, Yuliya, 1983, et al.
(författare)
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Properties of the 7He ground state from 8He neutron knockout
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 679:3, s. 191-196
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Tidskriftsartikel (refereegranskat)abstract
- The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the α+n relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a Iπ=1/2− state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.
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| 3. |
- Andersson, Pontus, 1971, et al.
(författare)
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Isobar Selective Laser Photodetachment In Trace Element Analysis
- 2009
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Ingår i: AIP Conference Proceedings. ; 1104
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Konferensbidrag (refereegranskat)abstract
- We are investigating the possibility to use laser photodetachment of negative ions as an isobaric selective filter in accelerator mass spectrometry (AMS). If successful, this method can be used to obtain higher sensitivity realized through better selectivity by suppression of molecular and/or elemental isobaric interference in different investigations using ultra rare isotopes in the 10−13 range and below.
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| 4. |
- Andersson, Pontus, 1971, et al.
(författare)
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Observation of the 2S1/2 metastable state in Pt−
- 2009
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Ingår i: PHYSICAL REVIEW A. - 1050-2947. ; 79, s. 022502 -
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Tidskriftsartikel (refereegranskat)abstract
- We have experimentally investigated the structure of the Pt− ion using laser photodetachment threshold spectroscopy. The experiment was conducted using a collinear laser-ion beam apparatus, in which the residual atoms created in the photodetachment process were detected. A p-wave threshold was observed in the photo- detachment spectrum at an energy of 6851͑13͒ cm−1. We conclude that this onset originates from a photode- tachment transition in which the initial state of Pt− is the previously unobserved 5d106s 2S1/2 state and the final state of Pt is the 5d96s 3D3 ground state. The excitation energy of the 2S1/2 state is determined to be 10 289͑13͒ cm−1. This value can be compared with a multiconfiguration Dirac-Fock calculation performed by Thøgersen et al. ͓Phys. Rev. Lett. 76, 2870 ͑1996͔͒, which yielded an excitation energy of 11 301 cm−1. Our data show no indication of the presence of any other state of Pt−. We conclude that the structure of the Pt− ion is now fully known.
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| 5. |
- Andersson, Pontus, 1971, et al.
(författare)
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The electron affinity of phosphorus
- 2007
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. ; 40:20, s. 4097-4107
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Forstner, O., et al.
(författare)
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Isobar suppression in AMS using laser photodetachment
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. ; 266:19-20, s. 4565-4568
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Tidskriftsartikel (refereegranskat)abstract
- We are investigating the possibility of using laser photodetachment of negative atomic and molecular ions as an additional isobaric selection filter in accelerator mass spectrometry. The aim of this study is to find a possibility to further improve the detection limit for long-lived heavy radionuclides at AMS facilities. We will focus on the astrophysical relevant radionuclide 182Hf, which is one of the isotopes measured with the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator) at the University of Vienna. Laser-induced isobar suppression is also of importance for radioactive-beam facilities. The present detection limit for measuring the isotope ratio 182Hf/Hf at VERA is 1×10-11. The limiting factor is the strong background of the stable isobar 182W. Currently this background is suppressed using suitable molecular ions in the injection stage. Selective laser photodetachment of the negative ions at the injector can lead to an additional suppression of the interfering isobar. Test experiments have been carried out at the negative ion laser spectroscopy setup at Göteborg University. In a small ion beam apparatus pulsed tunable laser radiation is used to measure the photodetachment cross-section of different atomic and molecular negative ions. We will present studies of the photodetachment process for various tungsten and hafnium molecules with the aim to find a selective isobaric suppression scheme using laser photodetachment spectroscopy in combination with AMS.
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| 7. |
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| 8. |
- Lindahl, Anton, 1982
(författare)
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Negative Ions Interacting with Photons and Electrons
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Negative ions are atoms or molecules where an extra electron is bound to neutral system. The nature of negative ions differs fundamentally from neutral and positive systems. The induced dipole potential responsible for the binding of the extra electron supports only a few bound states with relatively small binding energies. Since negative ions are so different from their neutral equivalents the methods used to study them are also fundamentally different. In this thesis the nature of negative ions is discussed and important properties of experimental investigations are presented. A general description of different experimental techniques is given, including a number of ion sources, and ways of confining and controlling the ions. Different reactions used to investigate the properties of the ions are discussed together with methods of detecting the reaction products. The focus is on photodetachment and electron collision experiments. A measurement of the absolute reaction cross sections for electron impact on Si2 − is presented as an example of a collision experiment. Three photodetachment studies are included in the thesis, where one have previously been published. Fundamental studies have been performed on P− and W− and refined values for the electron affinities are presented. WF5 − and HfF5 − have been investigated for the possibility of isobar selective photodetachment. With a laser based isobar filter the detection limit for 182 Hf in accelerator mass spectrometry measurements could be improved, but no suitable wavelength has so far been found. Experiments are presented in detail in the appended publications, with a summary of the experiments and the results in the main text. The results are compared with other types of measurements and results from other research groups.
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