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- Stone, Nicholas, et al.
(författare)
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A-priori calculations of hyperfine interactions in highly ionized atoms : g-factor measurements of pico-second states populated in nuclear reactions
- 2010
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Ingår i: Book of abstracts. ; , s. 65-65
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The recoil-in-vacuum [RIV] method, which uses attenuation of angular distributions to measure nuclear excited state g-factors, has been shown, in a recent experiment on a 132Te beam, to offer attractive possibilities for application with radioactive ion beams [RIBs] when combined with modern detector arrays [1]. The more usual Transient Field method struggles with limited beam intensity [2]. The magnetic hyperfine interaction acting on the nuclei of the recoiling ions was calibrated using states of known lifetime and g-factor. It is of clear importance to establish how these interactions vary with element and ionization state in order to discover how the RIV approach may be best utilized. The ability to calculate lifetimes and hyperfine interaction strengths in complex electronic levels of multiply ionized atoms has advanced markedly with modern computation techniques. Dirac-Hartree-Fock multi-configuration model [3] calculations, applied to systems ranging from 5-electron Fe ions to 23-electron Te ions will be presented. The results, compared with recent RIV experiments, show great promise that such calculations can provide parameter free, a-priori, calibrations for RIV experiments. The calculations are readily adapted to any nuclear level spin, allowing extension of measurement beyond the usual 2+, 4+ states of even-even isotopes to levels in odd-A and odd-odd isotopes. Projected experiments based not only on Coulomb excitation, but also on fusion reactions and fission fragments will be described.
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| 2. |
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| 3. |
- Stone, Nicholas J, et al.
(författare)
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G-factor measurements of picosecond states : opportunities and limitations of the recoil-in-vacuum method
- 2008
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Ingår i: Fission and properties of neutron-rich nuclei. - : World Scientific Publishing. ; , s. 379-389
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Konferensbidrag (refereegranskat)abstract
- This paper reports a new a-priori approach to the calibration of attenuations observed in Recoil-in-Vacuum angular distribution experiments which should allow extraction of g-factors for states of picosecond (ps) lifetime in many nuclei, of both odd-A and even-A without the need for extensive experimentally based calibration. The methods used and results for Ge and Mo isotopes are discussed, with outline applications to both on-line beam/target Coulomb excitation and fission fragment experiments.
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| 4. |
- Stuchbery, Andrew, et al.
(författare)
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Calibration of Recoil-In-Vacuum attenuations from first principles : comparison with recent experimental data on Fe isotopes
- 2015
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Ingår i: Hyperfine Interactions. - : Springer. - 0304-3843 .- 1572-9540. ; 230:1, s. 169-174
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Tidskriftsartikel (refereegranskat)abstract
- Precession of aligned nuclear spin systems in ions recoiling from the target into vacuum (RIV) with consequent attenuation of angular distributions of emitted radiation is, in principle, a versatile method for measurement of g-factors of nuclear excited states of lifetimes in the pico-second range (Stone et al., Phys. Rev. Lett., 94, 192501, 2005 and Stuchbery and Stone, Phys. Rev. C, 76, 034307, 2007). Calibration of the observed attenuations has been achieved in favourable cases through comparison with measurements on states having previously known g-factors and lifetimes. The general lack of suitable states with known g-factors has limited application of the RIV method. This paper concerns the present status of efforts to describe the states of excited ions recoiling into vacuum in detail so that the average interaction can be estimated with useful precision from a-priori theory. The calculations use the GRASP2K package (Froese-Fischer et al. 1997 and Jonsson, Comp. Phys. Comm., 177, 597, 2007 & 184, 2197, 2013) to obtain, for each recoiling ion change state, the individual possible electronic states, their configurations, lifetimes and hyperfine interactions. It is assumed that all possible ionic states are produced, up to a chosen excitation energy. This energy is selected to approximate the energy at which all states have lifetimes far shorter than the nuclear state of interest. It is further assumed that the ionic state total electron angular momenta are randomly oriented in space. The first estimates of the average attenuation of emission distributions, as a function of the product g τ of the nuclear state g-factor and mean lifetime, used an averaged precession frequency obtained neglecting transitions between electronic states. Improved calculations, which include such transitions, are described.
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