| 1. |
- Bak-Misiuk, J., et al.
(författare)
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Creation of MnAs nanoclusters during processing of GaMnAs
- 2009
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Ingår i: Radiation Physics And Chemistry. - : Elsevier BV. - 0969-806X. ; 78, s. 116-119
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Konferensbidrag (refereegranskat)abstract
- GaMnAs layers on (0 0 1)-oriented GaAs substrates were grown by the molecular beam epitaxy (MBE) method. Structural properties of samples processed at up to 920 K under hydrostatic Ar pressure up to 1.1 GPa were investigated by X-ray, secondary ion mass spectroscopy and atomic force microscopy methods. The sign of strain (compressive or tensile) of the GaMnAs layers, related to a creation of MnAs nanoclusters, is found to be dependent on processing conditions and on primary structure defects, whereas it was independent of Mn concentration. An influence of the defects structure in as-grown samples on the strain state of processed GaMnAs layers is discussed. (C) 2009 Elsevier Ltd. All rights reserved.
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| 2. |
- Brena, Barbara, et al.
(författare)
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Time-dependent DFT calculations of core electron shake-up states of metal-(free)-phthalocyanines
- 2006
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 75:11, s. 1578-1581
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Tidskriftsartikel (refereegranskat)abstract
- We have introduced a new approach for the calculation of the shake-up structures of molecular photoelectron spectra, based on the combination of time-dependent density functional theory (TD-DFT) and equivalent core hole (or Z + 1) approximation. The method, suitable for large molecules, has been applied to compute the complex shake-up states associated with the carbon Is X-ray photoelectron spectroscopy (XPS) of metal-free and nickel phthalocyanines (H2Pc and NiPc, respectively). A similar satellite profile emerges for both molecules.
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| 3. |
- Finell, Michael, et al.
(författare)
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Laboratory-scale production of biofuel pellets from electron beam treated Scots pine (Pinus silvestris L.) sawdust
- 2009
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 78, s. 281-287
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Tidskriftsartikel (refereegranskat)abstract
- The effect of electron beam (EB) treatment on pine sawdust used as raw material for fuel pellets was studied. Dry sawdust was EB treated at different dosage levels up to 100 kGy. The effect of EB treatment on fatty and resin acid composition was studied for different dosage levels and compared to untreated sawdust. Pellets were pressed in a laboratory single pellet press unit according to a D-optimal, response surface modeling (RSM) experimental design, where sawdust moisture content and die temperature were varied independently for EB treatment dosages of 0, 18.2 and 48.9 kGy. The responses of the designed experiment were density and strength for the produced pellets. The results showed that the free fatty and resin acid content in the sawdust initially decreased with increasing EB doses but at the highest EB doses it increased. The total content of extractives however initially increased and then decreased with increasing EB dose. Pellets made of EB treated sawdust had a significantly (at 95% confidence level) higher density and compressive strength than pellets made from untreated sawdust. EB treated sawdust behaved similarly to stored (mature) sawdust as a pellet raw material. Thus, EB treatment opens the possibility for controlled ageing (maturation) of pellet raw materials.
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| 4. |
- Gao, Bin, et al.
(författare)
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Studies of bromine modified single-walled carbon nanotubes using photoelectron spectroscopy and density-functional theory
- 2006
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 75:11, s. 1939-1942
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Tidskriftsartikel (refereegranskat)abstract
- Many applications based on single-walled carbon nanotubes (SWNTs) require chemical modification of carbon nanotube to optimize the functionalities of the device. In this contribution we discuss the properties of SWNTs immersed in a hydrobromic acid (HBr) solution. Changes of atomic and electronic structures of bromine modified SWNTs were investigated using photoelectron spectroscopy (PES). Spectra of SWNTs before and after immersion in the HBr solution exhibit different features. To understand the mechanism of interaction between SWNTs and bromine, we performed density-functional theory calculations to reveal the structural changes, adsorption energy and chemical bonding information of SWNTs interacting with bromine. In addition, based on the Gelius model, from the molecular orbitals (MOs), we calculated ultraviolet photoelectron spectra (UPS) of SWNTs with and without functionalizing and compared them with the experiment. The present study is a first step in the understanding of the functionalization mechanism of carbon nanotubes.
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| 5. |
- Lawniczak-Jablonska, K., et al.
(författare)
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The ratio of interstitial to substitutional site occupation by Mn atoms in GaAs estimated by EXAFS
- 2009
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 78, s. 80-85
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Konferensbidrag (refereegranskat)abstract
- The location of Mn atoms in the MBE-grown layers of Ga1-xMnxAs is correlated with all important physical properties of the final material, therefore, it is the subject of many studies. It is known that in the as-grown MBE samples the Mn atoms occupy substitutional and interstitial positions but the proportion between these sites is not easy to find. A powerful tool for this kind of study is XAS as it probes the local atomic order and the electronic structure. The EXAFS data analysis was performed considering superposition of possible Mn locations. This allowed for determination of the distribution of Mn between those two lattice sites. (C) 2009 Elsevier Ltd. All rights reserved.
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| 6. |
- Liljequist, David
(författare)
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A study of errors in trajectory simulation with relevance for 0.2 - 50 eV electrons in liquid water
- 2008
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 77:7, s. 835-853
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Tidskriftsartikel (refereegranskat)abstract
- A highly simplified model of the elastic scattering of electrons in a nm-size volume of liquid water, where the water molecules are regarded as point scatterers and inelastic scattering is neglected, is studied for electron energies 0.2–50 eV. This model allows an exact quantum mechanical solution of the multiple elastic scattering problem. The exact solutions are compared with the corresponding trajectory simulations. Two different data sets for the elastic scattering mean free path are discussed and used, one based on cross sections for water molecules in the gas phase and the other on cross sections derived from scattering in amorphous ice. In each case, the comparison provides a detailed insight into the character and magnitude of the error in the trajectory simulation, and gives a preliminary indication of an upper bound to the limits of validity of trajectory simulation in the real case of electron scattering in liquid water. Main results: with a fully random distribution of scatterers, the trajectory simulation is found to be a surprisingly good approximation down to quite low electron energies (). Below a few eV, the error increases rapidly with decreasing electron energy. A substantial increase of the error in trajectory simulation results when short-range order (minimum distance between scatterers) is introduced; the observed effect may partly be understood from the theory of kinematic diffraction in liquids. At very low electron energies (a few eV) one may note a quantum effect in the form of a standing wave pattern in the average distribution of scattering events.
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| 7. |
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| 8. |
- Paszkowicz, Wojciech, et al.
(författare)
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Silver behenate under high pressure: A powder diffraction study
- 2009
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 78, s. 105-108
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Konferensbidrag (refereegranskat)abstract
- Silver behenate, a salt of the behenic acid, known mostly for its applications in photothermographic imaging and use as a diffraction reference material, was studied by X-ray diffraction under pressures up to 11.4 GPa. Diffraction patterns were collected using a diamond anvil cell and synchrotron radiation at the 1711 beamline (MAXlab, Lund). The variation of the d spacing with pressure is determined and the potential usefulness of this dependence for pressure calibration is discussed. (C) 2009 Elsevier Ltd. All rights reserved.
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| 9. |
- Piszora, P., et al.
(författare)
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Synchrotron X-ray diffraction studies of LiMn2O4 and Li4Mn5O12 structures at high pressure
- 2009
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 78, s. 89-92
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Konferensbidrag (refereegranskat)abstract
- Experimental study of the phase transition in the lithium-excess lithium-manganese spinel over the pressure range 0-13 GPa has shown its suppression. This observation implies that the Li/Mn ratio, associated with the manganese oxidation state, plays an important role in the high-pressure phase transformation of the lithium-manganese spinels. As indicated by the results, the occupation of the octahedral sites with Li+ and Mn4+ ions stabilizes the crystallographic structure of this cubic spinel even at a high pressure. (C) 2009 Elsevier Ltd. All rights reserved.
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| 10. |
- Sankari, R, et al.
(författare)
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Update of the Finnish-Swedish beam line I411 at MAX-lab: Simulations of expected performance
- 2006
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Ingår i: Proceedings of the 20th International Conference on X-ray and Inner-Shell Processes (Radiation Physics and Chemistry). - : Elsevier BV. - 0969-806X. ; 75:11, s. 2000-2003
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Konferensbidrag (refereegranskat)abstract
- In the modified SX-700 monochromator installed at beam line I411, the focusing before the exit slit is achieved by a plane elliptical mirror. Like in the original SX-700 design, the resolution is mainly limited by the slope errors of the focusing mirror. A simple method to improve the resolution is to replace the focusing mirror by one with smaller slope errors. The effects of replacing the refocusing mirror by similar but more accurate in shape are studied both by carrying out ray tracing simulations and by analytical approach. Also the effect of replacing the grating was studied. (c) 2006 Elsevier Ltd. All rights reserved.
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| 11. |
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