| 1. |
- Makos, I., et al.
(författare)
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Attosecond photoelectron spectroscopy using high-harmonic generation and seeded free-electron lasers
- 2023
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Ingår i: 2023 Photonics North, PN 2023. - 9798350326734
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Konferensbidrag (refereegranskat)abstract
- In this work, we use attosecond time-resolved techniques to investigate photoionization dynamics on its natural timescale, employing both high harmonic generation and seeded free-electron lasers to generate extreme ultraviolet attosecond pulse trains for our studies. With the former approach, we examine the role of nuclear motion in molecular photoionization dynamics, while with the latter we introduce a novel attosecond timing tool for single-shot characterization of the relative phase between the XUV and the infrared field.
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| 2. |
- Maroju, P. K., et al.
(författare)
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Analysis of two-color photoelectron spectroscopy for attosecond metrology at seeded free-electron lasers
- 2021
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- The generation of attosecond pulse trains at free-electron lasers opens new opportunities in ultrafast science, as it gives access, for the first time, to reproducible, programmable, extreme ultraviolet (XUV) waveforms with high intensity. In this work, we present a detailed analysis of the theoretical model underlying the temporal characterization of the attosecond pulse trains recently generated at the free-electron laser FERMI. In particular, the validity of the approximations used for the correlated analysis of the photoelectron spectra generated in the two-color photoionization experiments are thoroughly discussed. The ranges of validity of the assumptions, in connection with the main experimental parameters, are derived.
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| 3. |
- Maroju, Praveen Kumar, et al.
(författare)
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Attosecond coherent control of electronic wave packets in two-colour photoionization using a novel timing tool for seeded free-electron laser
- 2023
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 17, s. 200-207
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Tidskriftsartikel (refereegranskat)abstract
- In ultrafast spectroscopy, the temporal resolution of time-resolved experiments depends on the duration of the pump and probe pulses, and on the control and characterization of their relative synchronization. Free-electron lasers operating in the extreme ultraviolet and X-ray spectral regions deliver pulses with femtosecond and attosecond duration in a broad array of pump-probe configurations to study a wide range of physical processes. However, this flexibility, together with the large dimensions and high complexity of the experimental set-ups, limits control of the temporal delay to the femtosecond domain, thus precluding a time resolution below the optical cycle. Here we demonstrate a novel single-shot technique able to determine the relative synchronization between an attosecond pulse train-generated by a seeded free-electron laser-and the optical oscillations of a near-infrared field, with a resolution of one atomic unit (24 as). Using this attosecond timing tool, we report the first example of attosecond coherent control of photoionization in a two-colour field by manipulating the phase of high-order near-infrared transitions.
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| 4. |
- Grinin, V. P., et al.
(författare)
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Modelling UX Ori star eclipses based on spectral observations with the Nordic Optical Telescope - I. RR Tau
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 524:3, s. 4047-4061
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Tidskriftsartikel (refereegranskat)abstract
- Based on observations obtained with the Nordic Optical Telescope (NOT) we investigate the spectral variability of the Herbig Ae star RR Tau. This star belongs to the UX Ori family, characterized by very deep fadings caused by the screening of the star with opaque fragments (clouds) of the protoplanetary discs. At the moments of such minima one observes strong spectral variability due to the fact that the dust cloud occults, for an observer, not only the star but also a part of the region where the emission spectrum originates. We calculated a series of obscuration models to interpret the observed variability of the H a line parameters. We consider two main obscuration scenarios: (1) the dust screen rises vertically above the circumstellar disc, and (2) the screen intersects the line-of-sight moving azimuthally with the disc. In both cases, the model of the emission region consists of a compact magnetosphere and a magnetocentrifugal disc wind. Comparison with observations shows that the first scenario explains well the variability of the radiation flux, the equivalent width, as well as the asymmetry of the H a line during eclipses, while the second scenario explains them only partly. This permits us to suggest that in the case of RR Tau, the main causes of the eclipses are either a structured disc wind, or the charged dust lifted along the field lines of the poloidal component of the magnetic field of the circumstellar disc.
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| 5. |
- Leubner, S., et al.
(författare)
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Hexahydroxytriphenylene for the synthesis of group 13 MOFs - a new inorganic building unit in a beta-cristobalite type structure
- 2020
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:10, s. 3088-3092
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Tidskriftsartikel (refereegranskat)abstract
- Two new, microporous MOFs of framework composition ((CH3)(2)NH2)(2)[M3O(HHTP)(HHTP center dot)], M = Al3+, Ga3+, H6HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene, are described. Electron diffraction combined with molecular simulations show that these compounds crystallize in the beta-cristobalite structure, containing a new type of trinuclear inorganic building unit for MOFs and radical anions.
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| 6. |
- Pihl, E., et al.
(författare)
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Ten new insights in climate science 2020- A horizon scan
- 2020
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Ingår i: Global Sustainability. - : Cambridge University Press. - 2059-4798.
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Tidskriftsartikel (refereegranskat)abstract
- Non-technical summary We summarize some of the past year's most important findings within climate change-related research. New research has improved our understanding of Earth's sensitivity to carbon dioxide, finds that permafrost thaw could release more carbon emissions than expected and that the uptake of carbon in tropical ecosystems is weakening. Adverse impacts on human society include increasing water shortages and impacts on mental health. Options for solutions emerge from rethinking economic models, rights-based litigation, strengthened governance systems and a new social contract. The disruption caused by COVID-19 could be seized as an opportunity for positive change, directing economic stimulus towards sustainable investments. Technical summary A synthesis is made of ten fields within climate science where there have been significant advances since mid-2019, through an expert elicitation process with broad disciplinary scope. Findings include: (1) a better understanding of equilibrium climate sensitivity; (2) abrupt thaw as an accelerator of carbon release from permafrost; (3) changes to global and regional land carbon sinks; (4) impacts of climate change on water crises, including equity perspectives; (5) adverse effects on mental health from climate change; (6) immediate effects on climate of the COVID-19 pandemic and requirements for recovery packages to deliver on the Paris Agreement; (7) suggested long-term changes to governance and a social contract to address climate change, learning from the current pandemic, (8) updated positive cost-benefit ratio and new perspectives on the potential for green growth in the short- A nd long-term perspective; (9) urban electrification as a strategy to move towards low-carbon energy systems and (10) rights-based litigation as an increasingly important method to address climate change, with recent clarifications on the legal standing and representation of future generations. Social media summary Stronger permafrost thaw, COVID-19 effects and growing mental health impacts among highlights of latest climate science.
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| 7. |
- Sandling, Johanna K., et al.
(författare)
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Molecular pathways in patients with systemic lupus erythematosus revealed by gene-centred DNA sequencing
- 2021
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 80:1, s. 109-117
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Systemic lupus erythematosus (SLE) is an autoimmune disease with extensive heterogeneity in disease presentation between patients, which is likely due to an underlying molecular diversity. Here, we aimed at elucidating the genetic aetiology of SLE from the immunity pathway level to the single variant level, and stratify patients with SLE into distinguishable molecular subgroups, which could inform treatment choices in SLE. Methods: We undertook a pathway-centred approach, using sequencing of immunological pathway genes. Altogether 1832 candidate genes were analysed in 958 Swedish patients with SLE and 1026 healthy individuals. Aggregate and single variant association testing was performed, and we generated pathway polygenic risk scores (PRS). Results: We identified two main independent pathways involved in SLE susceptibility: T lymphocyte differentiation and innate immunity, characterised by HLA and interferon, respectively. Pathway PRS defined pathways in individual patients, who on average were positive for seven pathways. We found that SLE organ damage was more pronounced in patients positive for the T or B cell receptor signalling pathways. Further, pathway PRS-based clustering allowed stratification of patients into four groups with different risk score profiles. Studying sets of genes with priors for involvement in SLE, we observed an aggregate common variant contribution to SLE at genes previously reported for monogenic SLE as well as at interferonopathy genes. Conclusions: Our results show that pathway risk scores have the potential to stratify patients with SLE beyond clinical manifestations into molecular subsets, which may have implications for clinical follow-up and therapy selection.
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