| 1. |
- Cedervall, Johan, et al.
(författare)
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Mössbauer study of the magnetocaloric compound AlFe2B2
- 2016
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 237
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Tidskriftsartikel (refereegranskat)abstract
- Mössbauer spectroscopy in the ferromagnetic AlFe2B2 reveals Tc=299 K and shows good agreement with magnetic measurements. The crystals are plate-shaped. The flakes are found from X-ray diffraction to be in the crystallographic ac-plane in the orthorhombic system. The axes of the principle electric field gradient tensor are, by symmetry, colinear with the crystal a-, b- and c-axes. By using information about the quadrupole splitting and line asymmetry in the paramagnetic regime together with the quadrupole shift of the resonance lines in the ferromagnetic regime the magnetic hyperfine field direction is found to be in the ab-plane having an angle =40° to the b-axis.
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| 2. |
- Difi, Siham, et al.
(författare)
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Role of iron in Na1.5Fe0.5Ti1.5(PO4)(3)/C as electrode material for Na-ion batteries studied by operando Mossbauer spectroscopy
- 2016
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540.
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Konferensbidrag (refereegranskat)abstract
- The role of iron in Na1.5Fe0.5Ti1.5(PO4)(3)/C electrode material for Na batteries has been studied by Fe-57 Mossbauer spectroscopy in operando mode. The potential profile obtained in the galvanostatic regime shows three plateaus at different voltages due to different reaction mechanisms. Two of them, at 2.2 and 0.3 V vs Na+/Na-0, have been associated to redox processes involving iron and titanium in Na1.5Fe0.5Ti1.5(PO4)(3). The role of titanium was previously elucidated for NaTi2(PO4)(3) and the effect of the substitution of Fe for Ti was investigated with 57Fe Mossbauer spectroscopy. We show that iron is an electrochemically active center at 2.2 V with the reversible Fe3+/Fe2+ transformation and then remains at the oxidation state Fe2+ along the sodiation until the end of discharge at 0 V.
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| 3. |
- Froelich, Piotr, et al.
(författare)
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Four-body treatment of the antihydrogen-positronium system : binding, structure, resonant states and collisions
- 2019
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Ingår i: Hyperfine Interactions. - : Springer. - 0304-3843 .- 1572-9540.
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Konferensbidrag (refereegranskat)abstract
- We have developed a coupled-rearrangement-channel method allowing the rigorous non-adiabatic treatment of the multi-channel scattering problem for four particles. We present the study of the binding, resonant and collisional properties of the (H) over bar -Ps system with the total angular momentum J = 0(+) (singlet positronic configuration). The binding energy, the life-times of the resonant states and the collisional cross sections are calculated and discussed. We present the preliminary cross sections for the elastic and inelastic (H) over bar -Ps scattering, notably for the excitation of Ps and for the rearrangement reaction producing the (H) over bar (+) ions.
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| 4. |
- Gismelseed, A. M., et al.
(författare)
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Investigations of Al-Dalang and Al-Hawashat meteorites
- 2016
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540.
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Konferensbidrag (refereegranskat)abstract
- Mossbauer spectroscopy, X-ray diffraction (XRD) measurements, and electron microprobe analysis (EMPA) have been performed on two meteorites named Al-Dalang and Al-Hawashat after identifying their falling sites in the Western region of Sudan. These two meteorites are ordinary chondrites with similar mineralogy. XRD and EMPA show that the two specimens consist of primary olivine, ortho-pyroxene and later crystallising clino-pyroxene as reaction rims against plagioclase. Fe-metal phases are dominated by kamacite (approximate to 6 wt.% Ni) and minor amounts of tetrataenite (approximate to 52 wt.% Ni). Troilite (FeS) and alabandite (MnS) are optically observed as sulphide phases. The Mossbauer measurements at 295 and 78 K are in agreement with the above characterizations, showing at least two paramagnetic doublets which are assigned to olivine and pyroxene and magnetic sextets assigned to kamacite (hyperfine field approximate to 33.5 T) and troilite FeS (hyperfine field approximate to 31 T).
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| 5. |
- Grzonka, D., et al.
(författare)
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Search for polarized antiproton production
- 2019
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Ingår i: Hyperfine Interactions. - : Springer Nature. - 0304-3843 .- 1572-9540. ; 240
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Tidskriftsartikel (refereegranskat)abstract
- The production of antiprotons is studied in view of possible polarization effects as basis for a polarized antiproton beam. If antiprotons are produced with some polarization, a quite simple procedure for the generation of a polarized antiproton beam could be worked out. The experiments are performed at the CERN PS test beam T11 where secondary particles with momenta around 3.5 GeV/c are selected. The polarization analysis is performed by measuring the asymmetry of the elastic (p) over barp-scattering in the Coulomb-nuclear interference region. The detection system includes Cherenkov and tracking detectors for the particle identification and the 3d track reconstruction. Details on the detection system and the status of the analysis are given.
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| 6. |
- Perez, P., et al.
(författare)
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The GBAR antimatter gravity experiment
- 2015
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; , s. 21-27
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Konferensbidrag (refereegranskat)abstract
- The GBAR project (Gravitational Behaviour of Anti hydrogen at Rest) at CERN, aims to measure the free fall acceleration of ultracold neutral anti hydrogen atoms in the terrestrial gravitational field. The experiment consists preparing anti hydrogen ions (one antiproton and two positrons) and sympathetically cooling them with Be (+) ions to less than 10 mu K. The ultracold ions will then be photo-ionized just above threshold, and the free fall time over a known distance measured. We will describe the project, the accuracy that can be reached by standard techniques, and discuss a possible improvement to reduce the vertical velocity spread.
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| 7. |
- 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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