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Publications (10 of 43) Show all publications
Ghosh, A., Jönsson, H. J., Mukkattukavil, D. J., Kvashnin, Y., Phuyal, D., Thunström, P., . . . Abdel-Hafiez, M. (2023). Magnetic circular dichroism in the dd excitation in the van der Waals magnet CrI3 probed by resonant inelastic x-ray scattering. Physical Review B, 107(11), Article ID 115148.
Open this publication in new window or tab >>Magnetic circular dichroism in the dd excitation in the van der Waals magnet CrI3 probed by resonant inelastic x-ray scattering
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 11, article id 115148Article in journal (Refereed) Published
Abstract [en]

We report on a combined experimental and theoretical study on CrI3 single crystals by employing the polarization dependence of resonant inelastic x-ray scattering (RIXS). Our investigations reveal multiple Cr 3d orbital splitting (dd excitations) as well as magnetic dichroism (MD) in the RIXS spectra. The dd excitation energies are similar on the two sides of the ferromagnetic transition temperature, T-C similar to 61 K, although MD in RIXS is predominant at 0.4 T magnetic field below TC. This demonstrates that the ferromagnetic superexchange interaction that is responsible for the interatomic exchange field is vanishingly small compared with the local exchange field that comes from exchange and correlation interaction among the interacting Cr 3d orbitals. The recorded RIXS spectra reported here reveal clearly resolved Cr 3d intraorbital dd excitations that represent transitions between electronic levels that are heavily influenced by dynamic correlations and multiconfiguration effects. Our calculations taking into account the Cr 3d hybridization with the ligand valence states and the full multiplet structure due to intra-atomic and crystal field interactions in Oh and D3d symmetry clearly reproduced the dichroic trend in experimental RIXS spectra.

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-500598 (URN)10.1103/PhysRevB.107.115148 (DOI)000961165700008 ()
Funder
Swedish Research Council, 2018-05973Swedish Foundation for Strategic ResearchKnut and Alice Wallenberg FoundationEU, European Research Council, 2018-05393EU, European Research Council, RIF14-0064EU, European Research Council, 854843-FASTCORREU, European Research Council, 2019-03569EU, European Research Council, 075-15-2021-604EU, European Research Council, 2021-03675Carl Tryggers foundation eSSENCE - An eScience CollaborationSwedish National Infrastructure for Computing (SNIC)Swedish Research Council, 2017-05030Swedish Research Council, 2021-03675Swedish Research Council, 2020-00681Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyEU, Horizon 2020, 824109
Available from: 2023-04-20 Created: 2023-04-20 Last updated: 2023-04-20Bibliographically approved
Agåker, M., Englund, C.-J., Sjöblom, P., Wassdahl, N., Fredriksson, P. & Såthe, C. (2021). An ultra-high-stability four-axis ultra-high-vacuum sample manipulator. Journal of Synchrotron Radiation, 28, 1059-1068
Open this publication in new window or tab >>An ultra-high-stability four-axis ultra-high-vacuum sample manipulator
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2021 (English)In: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 28, p. 1059-1068Article in journal (Refereed) Published
Abstract [en]

A report on a four-axis ultra-high-stability manipulator developed for use at the Veritas and Species RIXS beamlines at MAX IV Laboratory, Lund, Sweden, is presented. The manipulator consists of a compact, light-weight X-Y table with a stiffened Z tower carrying a platform with a rotary seal to which a manipulator rod holding the sample can be attached. Its design parameters have been optimized to achieve high eigen-frequencies via a light-weight yet stiff construction, to absorb forces without deformations, provide a low center of gravity, and have a compact footprint without compromising access to the manipulator rod. The manipulator system can house a multitude of different, easily exchangeable, manipulator rods that can be tailor-made for specific experimental requirements without having to rebuild the entire sample positioning system. It is shown that the manipulator has its lowest eigen-frequency at 48.5 Hz and that long-term stability is in the few tens of nanometres. Position accuracy is shown to be better than 100 nm. Angular accuracy is in the 500 nrad range with a long-term stability of a few hundred nanoradians.

Place, publisher, year, edition, pages
International Union Of CrystallographyINT UNION CRYSTALLOGRAPHY, 2021
Keywords
beamline, manipulator, high precision, ultra-high vacuum
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-452440 (URN)10.1107/S1600577521004859 (DOI)000670634000004 ()34212869 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilSwedish Foundation for Strategic Research , RIF14-0064
Available from: 2021-09-10 Created: 2021-09-10 Last updated: 2024-01-15Bibliographically approved
Barillot, T., Alexander, O., Cooper, B., Driver, T., Garratt, D., Li, S., . . . Kolorenc, P. (2021). Correlation-Driven Transient Hole Dynamics Resolved in Space and Time in the Isopropanol Molecule. Physical Review X, 11(3), Article ID 031048.
Open this publication in new window or tab >>Correlation-Driven Transient Hole Dynamics Resolved in Space and Time in the Isopropanol Molecule
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2021 (English)In: Physical Review X, E-ISSN 2160-3308, Vol. 11, no 3, article id 031048Article in journal (Refereed) Published
Abstract [en]

The possibility of suddenly ionized molecules undergoing extremely fast electron hole (or hole) dynamics prior to significant structural change was first recognized more than 20 years ago and termed charge migration. The accurate probing of ultrafast electron hole dynamics requires measurements that have both sufficient temporal resolution and can detect the localization of a specific hole within the molecule. We report an investigation of the dynamics of inner valence hole states in isopropanol where we use an x-ray pump-x-ray probe experiment, with site and state-specific probing of a transient hole state localized near the oxygen atom in the molecule, together with an ab initio theoretical treatment. We record the signature of transient hole dynamics and make the first tentative observation of dynamics driven by frustrated Auger-Meitner transitions. We verify that the effective hole lifetime is consistent with our theoretical prediction. This state-specific measurement paves the way to widespread application for observations of transient hole dynamics localized in space and time in molecules and thus to charge transfer phenomena that are fundamental in chemical and material physics.

Place, publisher, year, edition, pages
American Physical SocietyAmerican Physical Society (APS), 2021
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-455870 (URN)10.1103/PhysRevX.11.031048 (DOI)000692103200001 ()
Funder
EU, European Research Council, 2012-17Swedish Research Council, 2014-04518Swedish Research Council, 2018-04088Knut and Alice Wallenberg FoundationSwedish Research Council
Available from: 2021-10-18 Created: 2021-10-18 Last updated: 2024-01-17Bibliographically approved
Kjellsson, L., Ekholm, V., Agåker, M., Såthe, C., Pietzsch, A., Karlsson, H. O., . . . Rubensson, J.-E. (2021). Resonant inelastic x-ray scattering at the N2 π*-resonance: Lifetime-vibrational interference, radiative electron rearrangement, and wave-function imaging. Physical Review A. Atomic, Molecular, and Optical Physics, 103, Article ID 022812.
Open this publication in new window or tab >>Resonant inelastic x-ray scattering at the N2 π*-resonance: Lifetime-vibrational interference, radiative electron rearrangement, and wave-function imaging
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2021 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 103, article id 022812Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic x-ray scattering spectra excited at the pi*-resonance of the nitrogen molecule are presented. Well-resolved vibrational excitations in the electronic ground state, and in the 3 sigma g(-1 )1 pi(1)(g) a(1) Pi(g) state are observed. The spectra are analyzed within the Kramers-Heisenberg formalism, and the importance of lifetime-vibrational interference effects is highlighted. In addition, strongly dissociative multiply excited final states populated in radiative electron rearrangement are found in the valence ionization continua. The vibrational wave functions of the core-excited state are imaged on the strongly dissociative final state potentials.

Place, publisher, year, edition, pages
American Physical Society, 2021
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-433870 (URN)10.1103/PhysRevA.103.022812 (DOI)000617037900006 ()
Funder
Swedish Research Council, 2018-04088
Available from: 2021-02-03 Created: 2021-02-03 Last updated: 2021-03-26Bibliographically approved
Li, S., Driver, T., Al Haddad, A., Champenois, E. G., Agåker, M., Alexander, O., . . . Cryan, J. P. (2021). Two-dimensional correlation analysis for x-ray photoelectron spectroscopy. Journal of Physics B: Atomic, Molecular and Optical Physics, 54(14), Article ID 144005.
Open this publication in new window or tab >>Two-dimensional correlation analysis for x-ray photoelectron spectroscopy
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2021 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 54, no 14, article id 144005Article in journal (Refereed) Published
Abstract [en]

X-ray photoelectron spectroscopy (XPS) measures the binding energy of core-level electrons, which are well-localised to specific atomic sites in a molecular system, providing valuable information on the local chemical environment. The technique relies on measuring the photoelectron spectrum upon x-ray photoionisation, and the resolution is often limited by the bandwidth of the ionising x-ray pulse. This is particularly problematic for time-resolved XPS, where the desired time resolution enforces a fundamental lower limit on the bandwidth of the x-ray source. In this work, we report a novel correlation analysis which exploits the correlation between the x-ray and photoelectron spectra to improve the resolution of XPS measurements. We show that with this correlation-based spectral-domain ghost imaging method we can achieve sub-bandwidth resolution in XPS measurements. This analysis method enables XPS for sources with large bandwidth or spectral jitter, previously considered unfeasible for XPS measurements.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP)IOP Publishing, 2021
Keywords
x-ray photoelectron spectroscopy, free-electron laser, ghost imaging, AMO physics
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-452139 (URN)10.1088/1361-6455/abcdf1 (DOI)000684385400001 ()
Available from: 2021-09-06 Created: 2021-09-06 Last updated: 2024-01-15Bibliographically approved
Agåker, M., Mueller, F., Jensen, B. N., Åhnberg, K., Sjöblom, P., Deiwiks, J., . . . Såthe, C. (2020). A five-axis parallel kinematic mirror unit for soft X-ray beamlines at MAX IV. Journal of Synchrotron Radiation, 27, 262-271
Open this publication in new window or tab >>A five-axis parallel kinematic mirror unit for soft X-ray beamlines at MAX IV
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2020 (English)In: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 27, p. 262-271Article in journal (Refereed) Published
Abstract [en]

With the introduction of the multi-bend achromats in the new fourth-generation storage rings the emittance has decreased by an order of magnitude resulting in increased brightness. However, the higher brightness comes with smaller beam sizes and narrower radiation cones. As a consequence, the requirements on mechanical stability regarding the beamline components increases. Here an innovative five-axis parallel kinematic mirror unit for use with soft X-ray beamlines using off-axis grazing-incidence optics is presented. Using simulations and measurements from the HIPPIE beamline at the MAX IV Laboratory it is shown that it has no Eigen frequencies below 90 Hz. Its positioning accuracy is better than 25 nm linearly and 17-35 mu rad angularly depending on the mirror chamber dimensions.

Place, publisher, year, edition, pages
INT UNION CRYSTALLOGRAPHY, 2020
Keywords
beamline component, optics kinematics, soft X-ray, MAX IV
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-408533 (URN)10.1107/S160057751901693X (DOI)000519725000003 ()32153265 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilSwedish Foundation for Strategic Research , RIF14-0064
Available from: 2020-04-08 Created: 2020-04-08 Last updated: 2020-04-08Bibliographically approved
Parchenko, S., Paris, E., McNally, D., Abreu, E., Dantz, M., Bothschafter, E. M., . . . Staub, U. (2020). Orbital dynamics during an ultrafast insulator to metal transition. Physical Review Research, 2(2), Article ID 023110.
Open this publication in new window or tab >>Orbital dynamics during an ultrafast insulator to metal transition
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2020 (English)In: Physical Review Research, E-ISSN 2643-1564, Vol. 2, no 2, article id 023110Article in journal (Refereed) Published
Abstract [en]

We present ultrafast resonant inelastic x-ray scattering (RIXS) experiments performed at the vanadium L edge to track changes in the electronic structure of V2O3, a classical Mott-Hubbard material. The probed orbital excitations within the d shell of the V ion show a sub-ps time response, which evolves at later times to a state that appears electronically indistinguishable from the high-temperature metallic state. For low excitation fluences, a transient recovery or delay is observed, which could be related to a transient dimerization of the V-V bonds. Our results demonstrate the great potential for RIXS spectroscopy to study the ultrafast orbital dynamics in strongly correlated materials.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-433630 (URN)10.1103/PhysRevResearch.2.023110 (DOI)000602780200010 ()
Funder
EU, FP7, Seventh Framework Programme, 290605
Available from: 2021-02-01 Created: 2021-02-01 Last updated: 2021-06-11Bibliographically approved
Eichmann, U., Rottke, H., Meise, S., Rubensson, J.-E., Söderström, J., Agåker, M., . . . Ilchen, M. (2020). Photon-recoil imaging: Expanding the view of nonlinear x-ray physics. Science, 369(6511), 1630-1633
Open this publication in new window or tab >>Photon-recoil imaging: Expanding the view of nonlinear x-ray physics
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2020 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 369, no 6511, p. 1630-1633Article in journal (Refereed) Published
Abstract [en]

Addressing the ultrafast coherent evolution of electronic wave functions has long been a goal of nonlinear x-ray physics. A first step toward this goal is the investigation of stimulated x-ray Raman scattering (SXRS) using intense pulses from an x-ray free-electron laser. Earlier SXRS experiments relied on signal amplification during pulse propagation through dense resonant media. By contrast, our method reveals the fundamental process in which photons from the primary radiation source directly interact with a single atom. We introduce an experimental protocol in which scattered neutral atoms rather than scattered photons are detected. We present SXRS measurements at the neon K edge and a quantitative theoretical analysis. The method should become a powerful tool in the exploration of nonlinear x-ray physics.

Place, publisher, year, edition, pages
AMER ASSOC ADVANCEMENT SCIENCE, 2020
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-423594 (URN)10.1126/science.abc2622 (DOI)000574653300035 ()32973029 (PubMedID)
Funder
Swedish Research Council
Available from: 2020-10-28 Created: 2020-10-28 Last updated: 2020-10-28Bibliographically approved
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.
Open this publication in new window or tab >>Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning
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2017 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 8, article id 15461Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-327226 (URN)10.1038/ncomms15461 (DOI)000402745000001 ()28580940 (PubMedID)
Available from: 2017-08-25 Created: 2017-08-25 Last updated: 2023-03-28Bibliographically approved
Urpelainen, S., Sathe, C., Grizolli, W., Agåker, M., Head, A. R., Andersson, M., . . . Hennies, F. (2017). The SPECIES beamline at the MAX IV Laboratory: a facility for soft X-ray RIXS and APXPS. Paper presented at 9th International Workshop on X-Ray Radiation Damage to Biological Crystalline Samples, MAR 09-11, 2016, Lund, SWEDEN. Journal of Synchrotron Radiation, 24, 344-353
Open this publication in new window or tab >>The SPECIES beamline at the MAX IV Laboratory: a facility for soft X-ray RIXS and APXPS
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2017 (English)In: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 24, p. 344-353Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

SPECIES is an undulator-based soft X-ray beamline that replaced the old I511 beamline at the MAX II storage ring. SPECIES is aimed at high-resolution ambient-pressure X-ray photoelectron spectroscopy (APXPS), near-edge X-ray absorption fine-structure (NEXAFS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) experiments. The beamline has two branches that use a common elliptically polarizing undulator and monochromator. The beam is switched between the two branches by changing the focusing optics after the monochromator. Both branches have separate exit slits, refocusing optics and dedicated permanent endstations. This allows very fast switching between two types of experiments and offers a unique combination of the surface-sensitive XPS and bulk-sensitive RIXS techniques both in UHV- and at elevated ambient-pressure conditions on a single beamline. Another unique property of the beamline is that it reaches energies down to approximately 27 eV, which is not obtainable on other current APXPS beamlines. This allows, for instance, valence band studies under ambient-pressure conditions. In this article the main properties and performance of the beamline are presented, together with selected showcase experiments performed on the new setup.

Keywords
RIXS, APXPS, beamlines, MAX IV
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-315845 (URN)10.1107/S1600577516019056 (DOI)000391724900037 ()28009577 (PubMedID)
Conference
9th International Workshop on X-Ray Radiation Damage to Biological Crystalline Samples, MAR 09-11, 2016, Lund, SWEDEN
Funder
Swedish Research Council, 2009-5861Knut and Alice Wallenberg Foundation
Available from: 2017-02-21 Created: 2017-02-21 Last updated: 2017-11-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6501-5324

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