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Rubensson, Jan-Erik
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Liu, L., Huang, S., Vitos, L., Dong, M., Bykova, E., Zhang, D., . . . Lazor, P. (2019). Pressure-induced magnetovolume effect in CoCrFeAl high-entropy alloy. Communications Physics, 2, Article ID 42.
Öppna denna publikation i ny flik eller fönster >>Pressure-induced magnetovolume effect in CoCrFeAl high-entropy alloy
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2019 (Engelska)Ingår i: Communications Physics, E-ISSN 2399-3650, Vol. 2, artikel-id 42Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

High-entropy alloys (HEAs) composed of multiple-principal elements with (nearly) equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys. Spontaneously, one question emerges - would it be possible to synthesize a novel class of alloys combining the virtues of both CEAs and HEAs? Here, we report the pressure-induced magnetovolume effect in the body-centered-cubic CoCrFeAl HEA coupled with magnetic phase transitions from ferromagnetic to paramagnetic, and to non-magnetic states, originating from the successive collapses of local magnetic moments of Co and Fe. The observed magnetovolume anomalies, occurring in a progressive way, tailor appreciably the coefficient of thermal expansion of CoCrFeAl. These results further strengthen HEAs’ anticipated potential for designing multifunctional materials in virtue of their multiple outstanding properties, and reveal possible routes for their future synthesis.

Nationell ämneskategori
Den kondenserade materiens fysik Geovetenskap och miljövetenskap
Identifikatorer
urn:nbn:se:uu:diva-382796 (URN)10.1038/s42005-019-0141-9 (DOI)000467220700001 ()
Tillgänglig från: 2019-05-03 Skapad: 2019-05-03 Senast uppdaterad: 2019-11-25Bibliografiskt granskad
Chatzigeorgiou, E., Århammar, C., Gråsjö, J., Strömme, M. & Rubensson, J.-E. (2019). Resonant Inelastic X-ray Scattering on Mesoporous Magnesium Carbonate. In: The 40th International Conference on Vacuum Ultraviolet and X-ray Physics: . Paper presented at The 40th International Conference on Vacuum Ultraviolet and X-ray Physics, San Fransisco 2019. San Fransisco
Öppna denna publikation i ny flik eller fönster >>Resonant Inelastic X-ray Scattering on Mesoporous Magnesium Carbonate
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2019 (Engelska)Ingår i: The 40th International Conference on Vacuum Ultraviolet and X-ray Physics, San Fransisco, 2019Konferensbidrag, Muntlig presentation med publicerat abstract (Refereegranskat)
Ort, förlag, år, upplaga, sidor
San Fransisco: , 2019
Serie
Boreas. Uppsala Studies in Ancient Mediterranean and Near Eastern Civilizations, ISSN 0346-6442
Serie
VUVX
Nationell ämneskategori
Nanoteknik
Forskningsämne
Teknisk fysik med inriktning mot nanoteknologi och funktionella material
Identifikatorer
urn:nbn:se:uu:diva-389518 (URN)
Konferens
The 40th International Conference on Vacuum Ultraviolet and X-ray Physics, San Fransisco 2019
Tillgänglig från: 2019-07-16 Skapad: 2019-07-16 Senast uppdaterad: 2019-07-16
Chatzigeorgiou, E., Århammar, C., Gråsjö, J., Ekholm, V., Såthe, C., Olovsson, W., . . . Rubensson, J.-E. (2019). Soft X-ray Spectroscopy on  amorphous and crystalline magnesium carbonate. In: EUROMAT 2019: . Paper presented at EUROMAT 2019, 1-5 September 2019, Stockholm,. , Article ID 14135.
Öppna denna publikation i ny flik eller fönster >>Soft X-ray Spectroscopy on  amorphous and crystalline magnesium carbonate
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2019 (Engelska)Ingår i: EUROMAT 2019, 2019, artikel-id 14135Konferensbidrag, Muntlig presentation med publicerat abstract (Refereegranskat)
Nationell ämneskategori
Nanoteknik
Forskningsämne
Teknisk fysik med inriktning mot nanoteknologi och funktionella material
Identifikatorer
urn:nbn:se:uu:diva-395335 (URN)
Konferens
EUROMAT 2019, 1-5 September 2019, Stockholm,
Tillgänglig från: 2019-10-17 Skapad: 2019-10-17 Senast uppdaterad: 2019-10-17
Ekholm, V., Vazdar, M., Mason, P. E., Bialik, E., Walz, M.-M., Ohrwall, G., . . . Björneholm, O. (2018). Anomalous surface behavior of hydrated guanidinium ions due to ion pairing. Journal of Chemical Physics, 148(14), Article ID 144508.
Öppna denna publikation i ny flik eller fönster >>Anomalous surface behavior of hydrated guanidinium ions due to ion pairing
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2018 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, nr 14, artikel-id 144508Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Surface affinity of aqueous guanidinium chloride (GdmCl) is compared to that of aqueous tetrapropylammonium chloride (TPACl) upon addition of sodium chloride (NaCl) or disodium sulfate (Na2SO4). The experimental results have been acquired using the surface sensitive technique X-ray photoelectron spectroscopy on a liquid jet. Molecular dynamics simulations have been used to produce radial distribution functions and surface density plots. The surface affinities of both TPA(+) and Gdm(+) increase upon adding NaCl to the solution. With the addition of Na2SO4, the surface affinity of TPA(+) increases, while that of Gdm(+) decreases. From the results of MD simulations it is seen that Gdm(+) and SO42- ions form pairs. This finding can be used to explain the decreased surface affinity of Gdm(+) when co-dissolved with SO42- ions. Since SO42- ions avoid the surface due to the double charge and strong water interaction, the Gdm(+)-SO42- ion pair resides deeper in the solutions' bulk than the Gdm(+) ions. Since TPA(+) does not form ion pairs with SO42-, the TPA(+) ions are instead enriched at the surface.

Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:uu:diva-353201 (URN)10.1063/1.5024348 (DOI)000430128600034 ()29655316 (PubMedID)
Forskningsfinansiär
Vetenskapsrådet
Tillgänglig från: 2018-06-13 Skapad: 2018-06-13 Senast uppdaterad: 2018-09-02Bibliografiskt granskad
Ekholm, V., Caleman, C., Bjärnhall Prytz, N., Walz, M.-M., Werner, J., Öhrwall, G., . . . Björneholm, O. (2018). Strong Enrichment of Atmospherically Relevant Organic Ions at the Aqueous Interface: The Role of Ion Pairing and Cooperative Effects. Physical Chemistry, Chemical Physics - PCCP, 20(42), 27185-27191
Öppna denna publikation i ny flik eller fönster >>Strong Enrichment of Atmospherically Relevant Organic Ions at the Aqueous Interface: The Role of Ion Pairing and Cooperative Effects
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2018 (Engelska)Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 42, s. 27185-27191Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Surface affinity, orientation and ion pairing are investigated in mixed and single solute systems of aqueous sodium hexanoate and hexylammonium chloride. The surface sensitive X-ray photoelectron spectroscopy technique has been used to acquire the experimental results, while the computational data have been calculated using molecular dynamics simulations. By comparing the single solute solutions with the mixed one, we observe a non-linear surface enrichment and reorientation of the organic ions with their alkyl chains pointing out of the aqueous surface. We ascribe this effect to ion paring between the charged functional groups on the respective organic ion and hydrophobic expulsion of the alkyl chains from the surface in combination with van der Waals interactions between the alkyl chains. These cooperative effects lead to a substantial surface enrichment of organic ions, with consequences for aerosol surface properties.

Nationell ämneskategori
Atom- och molekylfysik och optik
Identifikatorer
urn:nbn:se:uu:diva-357368 (URN)10.1039/c8cp04525a (DOI)000451351500042 ()30339167 (PubMedID)
Forskningsfinansiär
Vetenskapsrådet, 2013-3940Vetenskapsrådet, 2014-04518Carl Tryggers stiftelse för vetenskaplig forskning
Tillgänglig från: 2018-08-15 Skapad: 2018-08-15 Senast uppdaterad: 2019-01-07Bibliografiskt granskad
Sanchez-Gonzalez, A., Micaelli, P., Olivier, C., Barillot, T. R., Ilchen, M., Lutman, A. A., . . . Marangos, J. P. (2017). Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning. Nature Communications, 8, Article ID 15461.
Öppna denna publikation i ny flik eller fönster >>Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning
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2017 (Engelska)Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, artikel-id 15461Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy, we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. This opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.

Ort, förlag, år, upplaga, sidor
Nature Publishing Group, 2017
Nationell ämneskategori
Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:uu:diva-327226 (URN)10.1038/ncomms15461 (DOI)000402745000001 ()28580940 (PubMedID)
Tillgänglig från: 2017-08-25 Skapad: 2017-08-25 Senast uppdaterad: 2017-11-29Bibliografiskt granskad
Zhang, L., Li, X., Augustsson, A., Lee, C. M., Rubensson, J.-E., Nordgren, J., . . . Guo, J.-H. -. (2017). Revealing the electronic structure of LiC6 by soft X-ray spectroscopy. Applied Physics Letters, 110(10), Article ID 104106.
Öppna denna publikation i ny flik eller fönster >>Revealing the electronic structure of LiC6 by soft X-ray spectroscopy
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2017 (Engelska)Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, nr 10, artikel-id 104106Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The electronic structure of LiC6 has been investigated by soft X-ray absorption and emission spectroscopies. The results reveal that upon full lithiation of graphite, the Li 2s electrons are transferred into the carbon pi* states in a near rigid-band behavior, resulting in the increased density of states near E-F and the shift of sigma* states to lower energies. In addition, the resonant inelastic X-ray scattering spectra of LiC6 do not show strong dispersive features as that of graphite, indicating that the crystal momentum is not conserved during the scattering process due to the delocalization of electrons in the intermediate state.

Nationell ämneskategori
Fysik Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:uu:diva-320659 (URN)10.1063/1.4978432 (DOI)000397871800063 ()
Tillgänglig från: 2017-06-30 Skapad: 2017-06-30 Senast uppdaterad: 2017-06-30Bibliografiskt granskad
Ertan, E., Kimberg, V., Gel'mukhanov, F., Hennies, F., Rubensson, J.-E., Schmitt, T., . . . Pietzsch, A. (2017). Theoretical simulations of oxygen K-edge resonant inelastic x-ray scattering of kaolinite. Physical Review B, 95(14), Article ID 144301.
Öppna denna publikation i ny flik eller fönster >>Theoretical simulations of oxygen K-edge resonant inelastic x-ray scattering of kaolinite
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2017 (Engelska)Ingår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, nr 14, artikel-id 144301Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Near-edge x-ray absorption fine structure (NEXAFS) and resonant inelastic x-ray scattering (RIXS) measurements at the oxygen K edge were combined with theoretical spectrum simulations, based on periodic density functional theory and nuclear quantum dynamics, to investigate the electronic structure and chemical bonding in kaolinite Al2Si2O5(OH)(4). We simulated NEXAFS spectra of all crystallographically inequivalent oxygen atoms in the crystal and RIXS spectra of the hydroxyl groups. Detailed insight into the ground-state potential energy surface of the electronic states involved in the RIXS process were accessed by analyzing the vibrational excitations, induced by the core excitation, in quasielastic scattering back to the electronic ground state. In particular, we find that the NEXAFS pre-edge is dominated by features related to OH groups within the silica and alumina sheets, and that the vibrational progression in RIXS can be used to selectively probe vibrational modes of this subclass of OH groups. The signal is dominated by the OH stretching mode, but also other lower vibrational degrees of freedom, mainly hindered rotational modes, contribute to the RIXS signal.

Ort, förlag, år, upplaga, sidor
AMER PHYSICAL SOC, 2017
Nationell ämneskategori
Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:uu:diva-322191 (URN)10.1103/PhysRevB.95.144301 (DOI)000399382500002 ()
Forskningsfinansiär
VetenskapsrådetCarl Tryggers stiftelse för vetenskaplig forskning EU, Europeiska forskningsrådet, 669531Knut och Alice Wallenbergs Stiftelse, KAW-2013.0020
Tillgänglig från: 2017-05-17 Skapad: 2017-05-17 Senast uppdaterad: 2017-11-29Bibliografiskt granskad
Couto, R. C., Guarise, M., Nicolaou, A., Jaouen, N., Chiuzbaian, G. S., Luening, J., . . . Simon, M. (2016). Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing. Scientific Reports, 6, Article ID 20947.
Öppna denna publikation i ny flik eller fönster >>Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing
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2016 (Engelska)Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 20947Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12-14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of "dark" with "bright" final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past.

Nationell ämneskategori
Atom- och molekylfysik och optik
Identifikatorer
urn:nbn:se:uu:diva-279560 (URN)10.1038/srep20947 (DOI)000369829300001 ()26860458 (PubMedID)
Forskningsfinansiär
Swedish National Infrastructure for Computing (SNIC), SNIC 2015/1-69Swedish National Infrastructure for Computing (SNIC), SNIC 023/07-18VetenskapsrådetKnut och Alice Wallenbergs StiftelseVetenskapsrådet
Tillgänglig från: 2016-03-02 Skapad: 2016-03-02 Senast uppdaterad: 2017-11-30Bibliografiskt granskad
Couto, R. C., Guarise, M., Nicolaou, A., Jaouen, N., Chiuzbaian, G. S., Luening, J., . . . Kimberg, V. (2016). Coupled electron-nuclear dynamics in resonant 1 sigma -> 2 pi x-ray Raman scattering of CO molecules. PHYSICAL REVIEW A, 93(3), Article ID 032510.
Öppna denna publikation i ny flik eller fönster >>Coupled electron-nuclear dynamics in resonant 1 sigma -> 2 pi x-ray Raman scattering of CO molecules
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2016 (Engelska)Ingår i: PHYSICAL REVIEW A, ISSN 2469-9926, Vol. 93, nr 3, artikel-id 032510Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present a detailed experimental-theoretical analysis of O K-edge resonant 1 sigma-2 pi inelastic x-ray scattering (RIXS) from carbon monoxide with unprecedented energy resolution. We employ high-level ab initio calculations to compute the potential energy curves of the states involved in the RIXS process and simulate the measured RIXS spectra using the wave-packet-propagation formalism, including Coulomb coupling in the final-state manifold. The theoretical analysis allows us to explain all the key features of the experimental spectra, including some that were not seen before. First, we clearly show the interference effect between different RIXS channels corresponding to the transition via orthogonal (1)Pi(x) and (1)Pi(y) core-excited states of CO. Second, the RIXS region of 13 eV energy loss presents a triple structure, revealed only by the high-resolution measurement. In previous studies, this region was attributed solely to a valence state. Here we show a strong Coulomb mixing of the Rydberg and valence final states, which opens the forbidden RIXS channels to the "dark" final Rydberg states and drastically changes the RIXS profile. Third, using a combination of high-resolution experiment and high-level theory, we improve the vertical bar 4 sigma(-1)2 pi(1)> final-state potential-energy curve by fitting its bottom part with the experiment. Also, the coupling constants between Rydberg and valence states were refined via comparison with the experiment. Our results illustrate the large potential of the RIXS technique for advanced studies of highly excited states of neutral molecules.

Nationell ämneskategori
Atom- och molekylfysik och optik
Identifikatorer
urn:nbn:se:uu:diva-286660 (URN)10.1103/PhysRevA.93.032510 (DOI)000372399100006 ()
Forskningsfinansiär
VetenskapsrådetKnut och Alice Wallenbergs Stiftelse
Tillgänglig från: 2016-04-27 Skapad: 2016-04-21 Senast uppdaterad: 2016-04-27Bibliografiskt granskad
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