| 1. |
- Abazov, V. M., et al.
(författare)
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The upgraded DO detector
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
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Tidskriftsartikel (refereegranskat)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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| 2. |
- Abazov, V. M., et al.
(författare)
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Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV using secondary vertex b tagging
- 2006
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:11, s. 112004-
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Tidskriftsartikel (refereegranskat)abstract
- We report a new measurement of the t (t) over bar production cross section in p (beta) over bar collisions at a center-of-mass energy of 1.96 TeV using events with one charged lepton (electron or muon), missing transverse energy, and jets. Using 425 pb(-1) of data collected using the D0 detector at the Fermilab Tevatron Collider, and enhancing the t (t) over bar content of the sample by tagging b jets with a secondary vertex tagging algorithm, the t (t) over bar production cross section is measured to be sigma(p (t) over bar -> t (t) over bar +X)=6.6 +/- 0.9(stat+syst) +/- 0.4(lum) pb. This cross section is the most precise D0 measurement to date for t (t) over bar production and is in good agreement with standard model expectations.
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| 3. |
- Went, M, et al.
(författare)
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Author Correction: Identification of multiple risk loci and regulatory mechanisms influencing susceptibility to multiple myeloma
- 2019
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1, s. 213-
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Tidskriftsartikel (refereegranskat)abstract
- The original version of this Article contained an error in the spelling of a member of the PRACTICAL Consortium, Manuela Gago-Dominguez, which was incorrectly given as Manuela Gago Dominguez. This has now been corrected in both the PDF and HTML versions of the Article. Furthermore, in the original HTML version of this Article, the order of authors within the author list was incorrect. The PRACTICAL consortium was incorrectly listed after Richard S. Houlston and should have been listed after Nora Pashayan. This error has been corrected in the HTML version of the Article; the PDF version was correct at the time of publication.
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| 4. |
- Went, M, et al.
(författare)
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Identification of multiple risk loci and regulatory mechanisms influencing susceptibility to multiple myeloma
- 2018
-
Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1, s. 3707-
-
Tidskriftsartikel (refereegranskat)abstract
- Genome-wide association studies (GWAS) have transformed our understanding of susceptibility to multiple myeloma (MM), but much of the heritability remains unexplained. We report a new GWAS, a meta-analysis with previous GWAS and a replication series, totalling 9974 MM cases and 247,556 controls of European ancestry. Collectively, these data provide evidence for six new MM risk loci, bringing the total number to 23. Integration of information from gene expression, epigenetic profiling and in situ Hi-C data for the 23 risk loci implicate disruption of developmental transcriptional regulators as a basis of MM susceptibility, compatible with altered B-cell differentiation as a key mechanism. Dysregulation of autophagy/apoptosis and cell cycle signalling feature as recurrently perturbed pathways. Our findings provide further insight into the biological basis of MM.
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| 5. |
- Berman, F., et al.
(författare)
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New grid scheduling and rescheduling methods in the GrADS Project
- 2005
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Ingår i: International journal of parallel programming. - : Springer Science and Business Media LLC. - 0885-7458 .- 1573-7640. ; 33:3-Feb, s. 209-229
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Tidskriftsartikel (refereegranskat)abstract
- The goal of the Grid Application Development Software (GrADS) Project is to provide programming tools and an execution environment to ease program development for the Grid. This paper presents recent extensions to the GrADS software framework: a new approach to scheduling workflow computations, applied to a 3-D image reconstruction application; a simple stop/migrate/restart approach to rescheduling Grid applications, applied to a QR factorization benchmark; and a process-swapping approach to rescheduling, applied to an N-body simulation. Experiments validating these methods were carried out on both the GrADS MacroGrid (a small but functional Grid) and the MicroGrid (a controlled emulation of the Grid).
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| 6. |
- Cooper, K., et al.
(författare)
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New Grid Scheduling and Rescheduling Methods in the GrADS Project
- 2004
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. The goal of the Grid Application Development Software (GrADS) project is to provide programming tools and an execution environment to ease program development for the grid. We present recent extensions to the GrADS software framework: 1. A new approach to scheduling workflow computations, applied to a 3D image reconstruction application; 2. A simple stop/migrate/restart approach to rescheduling grid applications, applied to a QR 3. A process-swapping approach to rescheduling, applied to an N-body simulation. Experiments validating these methods were carried out on both the GrADS MacroGrid (a small but functional grid) and the MicroGrid (a controlled emulation of the grid) and the results were demonstrated at the SC2003 conference.
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| 7. |
- Haugen, H.A., et al.
(författare)
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Infrastructure for CCS in the Skagerrak/Kattegat region, Southern Scandinavia: A feasibility study
- 2013
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 37, s. 2562-2569
-
Konferensbidrag (refereegranskat)abstract
- This paper gives an overview of results from a project which explored the feasibility of establishing a CO2 Capture and Storage infrastructure in the Skagerrak/Kattegat region of Southern Scandinavia. This involves assessment of the technical and economic parameters of the complete CCS chain and, in particular, identification of possible storage locations. The project ran from June 2009 to December 2011. Emissions from three major industrial clusters in the Skagerrak/Kattegat region - Gothenburg in Sweden, Grenland in Telemark County, southern Norway and Aalborg in Denmark - were targeted. Both emissions from process industries as well as power plants were included.
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| 8. |
- Sanchez-Gonzalez, A., et al.
(författare)
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Auger electron and photoabsorption spectra of glycine in the vicinity of the oxygen K-edge measured with an X-FEL
- 2015
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 48:23
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first measurement of the near oxygen K-edge auger spectrum of the glycine molecule. Our work employed an x-ray free electron laser as the photon source operated with input photon energies tunable between 527 and 547 eV. Complete electron spectra were recorded at each photon energy in the tuning range, revealing resonant and non-resonant auger structures. Finally ab initio theoretical predictions are compared with the measured above the edge auger spectrum and an assignment of auger decay channels is performed.
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| 9. |
- Ali, Mina, et al.
(författare)
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The multiple myeloma risk allele at 5q15 lowers ELL2 expression and increases ribosomal gene expression
- 2018
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1, s. 1649-
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, we identified ELL2 as a susceptibility gene for multiple myeloma (MM). To understand its mechanism of action, we performed expression quantitative trait locus analysis in CD138+ plasma cells from 1630 MM patients from four populations. We show that the MM risk allele lowers ELL2 expression in these cells (Pcombined = 2.5 × 10−27; βcombined = −0.24 SD), but not in peripheral blood or other tissues. Consistent with this, several variants representing the MM risk allele map to regulatory genomic regions, and three yield reduced transcriptional activity in plasmocytoma cell lines. One of these (rs3777189-C) co-locates with the best-supported lead variants for ELL2 expression and MM risk, and reduces binding of MAFF/G/K family transcription factors. Moreover, further analysis reveals that the MM risk allele associates with upregulation of gene sets related to ribosome biogenesis, and knockout/knockdown and rescue experiments in plasmocytoma cell lines support a cause–effect relationship. Our results provide mechanistic insight into MM predisposition.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Bernhardt, H., et al.
(författare)
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Debris flow recurrence periods and multi-temporal observations of colluvial fan evolution in central Spitsbergen (Svalbard)
- 2017
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X. ; 296, s. 132-141
-
Tidskriftsartikel (refereegranskat)abstract
- Fan-shaped accumulations of debris flow deposits are common landforms in polar regions such as Svalbard. Although depositional processes in these environments are of high interest to climate as well as Mars-analog research, several parameters, e.g., debris flow recurrence periods, remain poorly constrained. Here, we present an investigation based on remote sensing as well as in situ data of a similar to 0.4 km(2) large colluvial fan in Hanaskogdalen, central Spitsbergen. We analyzed high resolution satellite and aerial images covering five decades from 1961 to 2014 and correlated them with lichenometric dating as well as meteorological data. Image analyses and lichenometry deliver consistent results and show that the recurrence period of large debris flows (>= 400 m(3)) is about 5 to 10 years, with smaller flows averaging at two per year in the period from 2008 to 2013. While this is up to two orders of magnitude shorter than previous estimates for Svalbard (80 to 500 years), we found the average volume of -220 m(3) per individual flow to be similar to previous estimates for the region. Image data also reveal that an avulsion took place between 1961 and 1976, when the active part of the fan moved from its eastern to its western portion. A case study of the effects of a light rain event (similar to 5 mm/day) in the rainy summer of 2013, which triggered a large debris flow, further shows that even light precipitation can trigger major flows. This is made possible by multiple light rain events or gradual snow melt pre-saturating the permafrost ground and has to be taken into account when predicting the likelihood of potentially hazardous mass wasting in polar regions. Furthermore, our findings imply a current net deposition rate on the colluvial fan of similar to 480 m(3)/year, which is slightly less than the integrated net deposition rate of 576 to 720 m(3)/year resulting from the current fan volume divided by the 12,500 to 10,000 years since the onset of fan build-up after the area's deglaciation. However, the actual deposition rate, which should increase in a warmer climate including more rain, cannot be constrained due to effects like ongoing toe-cutting of the debris fan and some flows only causing internal redistributions.
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| 14. |
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| 15. |
- Eremina, R. M., et al.
(författare)
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Magnetization and specific heat of the dimer system CuTe(2)O(5)
- 2011
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Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 84:3, s. 391-395
-
Tidskriftsartikel (refereegranskat)abstract
- We report on magnetization and specific heat measurements on single-crystalline CuTe(2)O(5). The experimental data are directly compared to theoretical results for two different spin structures, namely an alternating spin-chain and a two-dimensional (2D) coupled dimer model, obtained by Das et al. [Phys. Rev. B 77, 224437 (2008)]. While the analysis of the specific heat does not allow to distinguish between the two models, the magnetization data is in good agreement with the 2D coupled dimer model.
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| 16. |
- Faergemann, Jan, 1948, et al.
(författare)
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Pentane-1,5-diol as a percutaneous absorption enhancer
- 2005
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Ingår i: Arch Dermatol Res. - : Springer Science and Business Media LLC. ; 297:6, s. 261-5
-
Tidskriftsartikel (refereegranskat)abstract
- Propylene glycol (propane-1,2-diol) is the only diol widely used in dermatology. Pentane-1,5-diol is mainly used as a plasticizer in cellulose products and adhesives, in dental composites and in brake fluid compositions and as a preservative for grain. However, pentane-1,5-diol is also an effective solvent, water-binding substance, antimicrobial agent and preservative and may therefore replace several ingredients in a skin composition. The release of tri-iodothyroacetic acid (TRIAC) and percutaneous absorption of hydrocortisone and mometasone furoate with either pentane-1,5-diol or propane-1,2-diol and 2-methyl-pentane-2,4-diol (hexylene glycol), respectively, as enhancers was compared. The release of TRIAC was 21% higher when pentane-1,5-diol was used as an enhancer instead of propane-1,2-diol. The percutaneous absorption of hydrocortisone through the skin was increased 12 times with propane-1,2-diol compared to 4.4 times with pentane-1,5-diol. However, the percutaneous absorption of hydrocortisone into the skin was 50% higher with pentane-1,5-diol compared to propane-1,2-diol. There was no significant difference, between the original mometasone furoate cream, with 2-methyl-pentane-2,4-diol, and the new cream with pentane-1,5-diol in the amount of mometasone furoate that was absorbed into the skin and through the skin. However, the cosmetic properties of the new mometasone furoate cream was superior to the original mometasone furoate cream, for examples, no bad odour, more even texture, goes better into the skin and has less greasiness. Pentane-1,5-diol can be used as a technology platform, which adds a series of desirable properties to dermatological preparations and enhances product usability. This will result in improved formulations for a series of major and commonly used dermatological drugs. When used in pharmaceutical topical preparations, pentane-1,5-diol will increase the percutaneous absorption of the active substance and it is an efficient antimicrobial agent that will act as an effective preservative in topical formulations. Pentane-1,5-diol is cosmetically attractive, has low risk for skin and eye irritation compared to other diols, low toxicity risk and no bad odour.
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| 17. |
- Fukuzawa, H., et al.
(författare)
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Deep Inner-Shell Multiphoton Ionization by Intense X-Ray Free-Electron Laser Pulses
- 2013
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:17
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that Xen+ with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n >= 24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers. DOI: 10.1103/PhysRevLett.110.173005
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| 18. |
- Fukuzawa, H., et al.
(författare)
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Electron spectroscopy of rare-gas clusters irradiated by x-ray free-electron laser pulses from SACLA
- 2016
-
Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 49:3
-
Tidskriftsartikel (refereegranskat)abstract
- We have measured electron energy spectra and asymmetry parameters of Ar clusters and Xe clusters illuminated by intense x-rays at 5 and 5.5 keV. A velocity map imaging spectrometer was developed for this purpose and employed at an x-ray free-electron laser facility, SACLA in Japan. The cluster size dependence and the peak fluence dependence of the electron spectra and asymmetry parameters are discussed.
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| 19. |
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| 20. |
- Gryzlova, E. V., et al.
(författare)
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Doubly resonant three-photon double ionization of Ar atoms induced by an EUV free-electron laser
- 2011
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 84:6
-
Tidskriftsartikel (refereegranskat)abstract
- A mechanism for three-photon double ionization of atoms by extreme-ultraviolet free-electron laser pulses is revealed, where in a sequential process the second ionization step, proceeding via resonant two-photon ionization of ions, is strongly enhanced by the excitation of ionic autoionizing states. In contrast to the conventional model, the mechanism explains the observed relative intensities of photoelectron peaks and their angular dependence in three-photon double ionization of argon.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Johnsson, Magnus, 1983, et al.
(författare)
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Serum neurofilament light for detecting disease activity in individual patients in multiple sclerosis: A 48-week prospective single-center study
- 2024
-
Ingår i: MULTIPLE SCLEROSIS JOURNAL. - 1352-4585 .- 1477-0970.
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Serum neurofilament light (sNfL) reflects neuroaxonal damage and is now used as an outcome in treatment trials of relapsing-remitting multiple sclerosis (RRMS). However, the diagnostic properties of sNfL for monitoring disease activity in individual patients warrant further investigations. Method: Patients with suspected relapse and/or contrast-enhancing lesions (CELs) were consecutively included and performed magnetic resonance imaging (MRI) of the brain at baseline and weeks 28 and 48. Serum was obtained at baseline and 2, 4, 8, 16, 24, and 48 weeks. Neurofilament light concentration was measured using Single molecule array technology. Results: We included 44 patients, 40 with RRMS and 4 with clinically isolated syndrome. The median sNfL level peaked at 2 weeks post-baseline (14.6 ng/L, interquartile range (IQR); 9.3-31.6) and reached nadir at 48 weeks (9.1 ng/L, IQR; 5.5-15.0), equivalent to the median sNfL of controls (9.1 ng/L, IQR; 7.4-12). A baseline Z-score of more than 1.1 (area under the curve; 0.78, p < 0.0001) had a sensitivity of 81% and specificity of 70% to detect disease activity. Conclusion: One out of five patients with relapse and/or CELs did not change significantly in post-baseline sNfL levels. The utility of repeated sNfL measurements to monitor disease activity is complementary rather than a substitute for clinical and MRI measures.
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| 30. |
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| 31. |
- Ma, R., et al.
(författare)
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Photoelectron angular distributions for the two-photon ionization of helium by ultrashort extreme ultraviolet free-electron laser pulses
- 2013
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16
-
Tidskriftsartikel (refereegranskat)abstract
- The two-photon ionization of helium atoms by ultrashort extreme-ultraviolet free-electron laser pulses, produced by the SPring-8 Compact SASE Source test accelerator, was investigated at photon energies of 20.3, 21.3, 23.0 and 24.3 eV. The angular distribution of photoelectrons generated by two-photon ionization is obtained using a velocity map imaging spectrometer. The phase-shift differences and amplitude ratios of the outgoing s and d continuum wave packets are extracted from the photoelectron angular distributions. The obtained values of the phase-shift differences are distinct from scattering phase-shift differences when the photon energy is tuned to a resonance with an excited level or Rydberg manifold. The difference stems from the co-presence of resonant and non-resonant path contributions in the two-photon ionization by femtosecond pulses. Since the relative contribution of both paths can be controlled in principle by the pulse shape, these results illustrate a new way to tailor the continuum wave packet.
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| 32. |
- Maclot, Sylvain, et al.
(författare)
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Photodissociation dynamics of the diamondoid adamantane induced by attosecond XUV pulses
- 2020
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Ingår i: 31st international conference on photonic, electronic and atomic collisions (icpeac xxxi). - : IOP Publishing. ; 1412
-
Konferensbidrag (refereegranskat)abstract
- Adamantane is the simplest of the diamondoid molecules, which due to their high stability are of high interest both in astrophysics and nanotechnology. This work investigates the molecular photodissociation after ionization by attosecond XUV pulses. The fragmentation dynamics is inferred by means of velocity map imaging spectrometry, covariance analysis techniques and quantum chemistry calculations.
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| 33. |
- Manschwetus, B., et al.
(författare)
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Two-photon double ionization of neon studied with intense attosecond pulse trains
- 2016
-
Ingår i: International Conference on Ultrafast Phenomena, UP 2016. - 9781943580187 ; Part F20-UP 2016
-
Konferensbidrag (refereegranskat)abstract
- We focused an intense attosecond pulse train into a neon gas target and observed Ne2+ resulting from two-photon double ionization. By modifying the photon spectrum we find that the process is dominated by the sequential ionization via the Ne+ ion.
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| 34. |
- Manschwetus, B., et al.
(författare)
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Two-photon double ionization of neon using an intense attosecond pulse train
- 2016
-
Ingår i: Physical Review A. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 93:6
-
Tidskriftsartikel (refereegranskat)abstract
- We present a demonstration of two-photon double ionization of neon using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a photon energy regime where both direct and sequential mechanisms are allowed. For an APT generated through high-order harmonic generation (HHG) in argon we achieve a total pulse energy close to 1μJ, a central energy of 35 eV, and a total bandwidth of ∼30 eV. The APT is focused by broadband optics in a neon gas target to an intensity of 3×1012Wcm−2. By tuning the photon energy across the threshold for the sequential process the double ionization signal can be turned on and off, indicating that the two-photon double ionization predominantly occurs through a sequential process. The demonstrated performance opens up possibilities for future XUV-XUV pump-probe experiments with attosecond temporal resolution in a photon energy range where it is possible to unravel the dynamics behind direct versus sequential double ionization and the associated electron correlation effects.
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| 35. |
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| 36. |
- Mazzetti, M.J., et al.
(författare)
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NORDICCS CCS roadmap
- 2014
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 51, s. 1-13
-
Konferensbidrag (refereegranskat)abstract
- The Nordic CCS roadmap is developed in the NORDICCS project, a collaborative research project between leading CCS research institutions in the five Nordic countries. The roadmap will outline jointly developed Nordic strategies for widespread implementation of CCS in the Nordic countries in order to help Nordic industries meet a carbon constrained future with a high price on carbon emissions. It will identify pathways and milestones for large-scale Nordic implementation of CCS resulting in beneficial economies of scale that will increase the likelihood of implementation. Several novel cases will be presented that reveal future Nordic opportunities, including industrial CCS where emitters have large point sources of CO2 localized in clusters, and natural gas sweetening with the potential for use of Enhanced Oil Recovery (EOR) to defray the costs. Recommendations will be made for actions relating to joint political work in the Nordic region for improving the framework conditions for CCS.
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| 37. |
- Mondal, S., et al.
(författare)
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Photoelectron angular distributions for the two-photon sequential double ionization of xenon by ultrashort extreme ultraviolet free electron laser pulses
- 2013
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16
-
Tidskriftsartikel (refereegranskat)abstract
- Xenon atoms are double-ionized by sequential two-photon absorption by ultrashort extreme ultraviolet free-electron laser pulses with a photon energy of 23.0 and 24.3 eV, produced by the SPring-8 Compact SASE Source test accelerator. The angular distributions of photoelectrons generated by two-photon double ionization are obtained using velocity map imaging. The results are reproduced reasonably well by the present theoretical calculations within the multi-configurational Dirac-Fock approach.
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| 38. |
- Motomura, K., et al.
(författare)
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Sequential multiphoton multiple ionization of atomic argon and xenon irradiated by X-ray free-electron laser pulses from SACLA
- 2013
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated multiphoton multiple ionization of argon and xenon atoms at 5 keV using a new x-ray free electron laser (XFEL) facility, the SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan. The experimental results are compared with the new theoretical results presented here. The absolute fluence of the XFEL pulse has been determined with the help of the calculations utilizing two-photon processes in the argon atom. The high charge states up to +22 observed for Xe in comparison with the calculations point to the occurrence of sequential L-shell multiphoton absorption and of resonance-enabled x-ray multiple ionization.
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| 39. |
- Neoričić, L., et al.
(författare)
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Resonant two-photon ionization of helium atoms studied by attosecond interferometry
- 2022
-
Ingår i: Frontiers in Physics. - : Frontiers Media SA. - 2296-424X. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- We study resonant two-photon ionization of helium atoms via the 1s3p, 1s4p and 1s5p P-1(1) states using the 15(th) harmonic of a titanium-sapphire laser for the excitation and a weak fraction of the laser field for the ionization. The phase of the photoelectron wavepackets is measured by an attosecond interferometric technique, using the 17(th) harmonic. We perform experiments with angular resolution using a velocity map imaging spectrometer and with high energy resolution using a magnetic bottle electron spectrometer. Our results are compared to calculations using the two-photon random phase approximation with exchange to account for electron correlation effects. We give an interpretation for the multiple pi-rad phase jumps observed, both at and away from resonance, as well as their dependence on the emission angle.
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| 40. |
- Oberst, J., et al.
(författare)
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Planetary polar explorer – the case for a next-generation remote sensing mission to low Mars orbit
- 2022
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 54, s. 695-711
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Tidskriftsartikel (refereegranskat)abstract
- We propose the exploration of polar areas on Mars by a next-generation orbiter mission. In particular, we aim at studying the seasonal and regional variations in snow-deposits, which – in combination with measurements of temporal variations in rotation and gravity field – will improve models of the global planetary CO2 cycle. A monitoring of polar scarps for rock falls and avalanche events may provide insights into the dynamics of ice sheets. The mapping of the complex layering of polar deposits, believed to contain an important record of climate history, may help us understand the early climate collapse on the planet. Hence, we propose an innovative next-generation exploration mission in polar circular Low Mars Orbit, which will be of interest to scientists and challenging to engineers alike. Schemes will be developed to overcome atmosphere drag forces acting upon the spacecraft by an electric propulsion system. Based on the experience of missions of similar type in Earth orbit we believe that a two-year mission in circular orbit is possible at altitudes as low as 150 km. Such a mission opens new opportunities for novel remote sensing approaches, not requiring excessive telescope equipment or power. We anticipate precision altimetry, powerful radars, high-resolution imaging, and magnetic field mapping. © 2022, The Author(s).
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| 41. |
- Oliveira, M. H. de Andrade, et al.
(författare)
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Soot, PAH and OH measurements in vaporized liquid fuel flames
- 2013
-
Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 112, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- Qualitative measurements of both OH and polycyclic aromatic hydrocarbons (PAH) as well as quantitative data of soot volume fraction f(v) have been obtained in vaporized liquid fuels, with the main goal of providing experimental data for combustion models and numerical mechanism validation. Measurements were carried out in a laminar coflow burner which was designed, built and integrated with an evaporation system, enabling the combustion of vaporized liquid fuels at pressures of up to 3.0 MPa to be studied. The fuels n-heptane and n-decane, referred to in the literature as being important surrogate fuels, were selected for measurements at atmospheric pressure that were carried out in the experimental setup described, making use of a combination of the Laser Induced Fluorescence (LIF) and Laser Induced Incandescence (LII) techniques. Partially premixed flames of n-heptane and n-decane showed similar combustion characteristics in the range of 1.9 < phi < 3.7. For both of the fuels the threshold for soot formation was found to be at about phi similar to 3.3. Comparison of the LIF and LII measurements for the n-heptane flames within the range of 3.7 <= phi <= 8.5 indicated the maximum PAH LIF signal to be a good predictor of f(vmax) obtained from LII. Excitation at 266 nm using delayed detection was found to result in the signals obtained showing a close linear correlation with the soot volume fraction obtained from LII when prompt detection at 1064 nm excitation was used. Neither the effects of any additional photo-chemical processes making use of high laser power at 266 nm nor the effects of particle size on the delayed gate times appeared to be of any significance for the flame conditions studied here. (C) 2013 Elsevier Ltd. All rights reserved.
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| 42. |
- Rolles, D., et al.
(författare)
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Femtosecond x-ray photoelectron diffraction on gas-phase dibromobenzene molecules
- 2014
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 47:12
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Tidskriftsartikel (refereegranskat)abstract
- We present time-resolved femtosecond photoelectron momentum images and angular distributions of dissociating, laser-aligned 1,4-dibromobenzene (C6H4Br2) molecules measured in a near-infrared pump, soft-x-ray probe experiment performed at an x-ray free-electron laser. The observed alignment dependence of the bromine 2p photoelectron angular distributions is compared to density functional theory calculations and interpreted in terms of photoelectron diffraction. While no clear time-dependent effects are observed in the angular distribution of the Br(2p) photoelectrons, other, low-energy electrons show a pronounced dependence on the time delay between the near-infrared laser and the x-ray pulse.
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| 43. |
- Rouzee, A., et al.
(författare)
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Towards imaging of ultrafast molecular dynamics using FELs
- 2013
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16
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Tidskriftsartikel (refereegranskat)abstract
- The dissociation dynamics induced by a 100 fs, 400 nm laser pulse in a rotationally cold Br-2 sample was characterized by Coulomb explosion imaging (CEI) using a time-delayed extreme ultra-violet (XUV) FEL pulse, obtained from the Free electron LASer in Hamburg (FLASH). The momentum distribution of atomic fragments resulting from the 400 nm-induced dissociation was measured with a velocity map imaging spectrometer and used to monitor the internuclear distance as the molecule dissociated. By employing the simultaneously recorded in-house timing electro-optical sampling data, the time resolution of the final results could be improved to 300 fs, compared to the inherent 500 fs time-jitter of the FEL pulse. Before dissociation, the Br-2 molecules were transiently 'fixed in space' using laser-induced alignment. In addition, similar alignment techniques were used on CO2 molecules to allow the measurement of the photoelectron angular distribution (PAD) directly in the molecular frame (MF). Our results on MFPADs in aligned CO2 molecules, together with our investigation of the dissociation dynamics of the Br-2 molecules with CEI, show that information about the evolving molecular structure and electronic geometry can be retrieved from such experiments, therefore paving the way towards the study of complex non-adiabatic dynamics in molecules through XUV time-resolved photoion and photoelectron spectroscopy.
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Stern, S., et al.
(författare)
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Toward atomic resolution diffractive imaging of isolated molecules with X-ray free-electron lasers
- 2014
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Ingår i: Faraday Discussions. - : Royal Society of Chemistry (RSC). - 1364-5498. ; 171, s. 393-418
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Tidskriftsartikel (refereegranskat)abstract
- We give a detailed account of the theoretical analysis and the experimental results of an X-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gasphase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Coherent Light Source [Phys. Rev. Lett. 112, 083002 (2014)]. This experiment is the first step toward coherent diffractive imaging of structures and structural dynamics of isolated molecules at atomic resolution, i.e., picometers and femtoseconds, using X-ray free-electron lasers.
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| 48. |
- Tachibana, T., et al.
(författare)
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Nanoplasma Formation by High Intensity Hard X-rays
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at similar to 5 keV. Our experiment was carried out at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with the molecular dynamics tool XMDYN. We found that in this unprecedented wavelength regime nanoplasma formation is a highly indirect process. In the argon clusters investigated, nanoplasma is mainly formed through secondary electron cascading initiated by slow Auger electrons. Energy is distributed within the sample entirely through Auger processes and secondary electron cascading following photoabsorption, as in the hard x-ray regime there is no direct energy transfer from the field to the plasma. This plasma formation mechanism is specific to the hard-x-ray regime and may, thus, also be important for XFEL-based molecular imaging studies. In xenon clusters, photo-and Auger electrons contribute more significantly to the nanoplasma formation. Good agreement between experiment and simulations validates our modelling approach. This has wide-ranging implications for our ability to quantitatively predict the behavior of complex molecular systems irradiated by high-intensity hard x-rays.
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| 49. |
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| 50. |
- Veyrinas, K., et al.
(författare)
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Chromatic aberrations correction of attosecond high-order harmonic beams by flat-top spatial shaping of the fundamental beam
- 2023
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 25:2
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Tidskriftsartikel (refereegranskat)abstract
- Attosecond pulses created by high-order harmonic generation in gases often exhibit strong chromatic aberrations, arising from the broad bandwidth and wavelength-dependent nonlinear light-matter interaction. When the driving laser intensity varies spatially, as for Gaussian driving beams, the apparent source position of the harmonics differs significantly from one order to the next, thus affecting the achievable intensity and duration of the attosecond pulses when they are focused on a target. We show that these chromatic aberrations can be reduced by spatially shaping the fundamental beam to generate high-order harmonics with a driver having a flat-top profile inside the gas medium. By measuring both the intensity profile and wavefront for each harmonic in a plane, we access the extreme ultra-violet (XUV) beam properties and investigate these properties near focus. We observe that controlling chromatic aberrations by flat-top spatial shaping strongly reduces the variation of the XUV spectrum on the beam axis during propagation and, in return, the longitudinal sensitivity of both the temporal profiles and the temporal shifts of the focused attosecond pulses.
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