| 1. |
- Adrian-Martinez, S., et al.
(författare)
-
A first search for coincident gravitational waves and high energy neutrinos using LIGO, Virgo and ANTARES data from 2007
- 2013
-
Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :6
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.
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| 2. |
- Aasi, J., et al.
(författare)
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Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data
- 2013
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 87:4
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50, 1190] Hz and with frequency derivative range of similar to[-20, 1.1] x 10(-10) Hz s(-1) for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we report upper limits on the intrinsic gravitational wave strain amplitude h(0). For example, in the 0.5 Hz-wide band at 152.5 Hz, we can exclude the presence of signals with h(0) greater than 7.6 x 10(-25) at a 90% confidence level. This search is about a factor 3 more sensitive than the previous Einstein@Home search of early S5 LIGO data.
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| 3. |
- Aasi, J., et al.
(författare)
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The characterization of Virgo data and its impact on gravitational-wave searches
- 2012
-
Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 1361-6382 .- 0264-9381. ; 29:15
-
Tidskriftsartikel (refereegranskat)abstract
- Between 2007 and 2010 Virgo collected data in coincidence with the LIGO and GEO gravitational-wave (GW) detectors. These data have been searched for GWs emitted by cataclysmic phenomena in the universe, by non-axisymmetric rotating neutron stars or from a stochastic background in the frequency band of the detectors. The sensitivity of GW searches is limited by noise produced by the detector or its environment. It is therefore crucial to characterize the various noise sources in a GW detector. This paper reviews the Virgo detector noise sources, noise propagation, and conversion mechanisms which were identified in the three first Virgo observing runs. In many cases, these investigations allowed us to mitigate noise sources in the detector, or to selectively flag noise events and discard them from the data. We present examples from the joint LIGO-GEO-Virgo GW searches to show how well noise transients and narrow spectral lines have been identified and excluded from the Virgo data. We also discuss how detector characterization can improve the astrophysical reach of GW searches.
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| 4. |
- Evans, P. A., et al.
(författare)
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Swift Follow-up Observations of Candidate Gravitational-wave Transient Events
- 2012
-
Ingår i: The Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 203:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them is consistent with background and the other one was a test, part of a "blind injection challenge." With this work we demonstrate the feasibility of rapid follow-ups of GW transients and establish the sensitivity improvement joint electromagnetic and GW observations could bring. This is a first step toward an electromagnetic follow-up program in the regime of routine detections with the advanced GW instruments expected within this decade. In that regime, multi-wavelength observations will play a significant role in completing the astrophysical identification of GW sources. We present the methods and results from this first combined analysis and discuss its implications in terms of sensitivity for the present and future instruments.
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| 5. |
- Aasi, J., et al.
(författare)
-
Parameter estimation for compact binary coalescence signals with the first generation gravitational-wave detector network
- 2013
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 88:6
-
Tidskriftsartikel (refereegranskat)abstract
- Compact binary systems with neutron stars or black holes are one of the most promising sources for ground-based gravitational-wave detectors. Gravitational radiation encodes rich information about source physics; thus parameter estimation and model selection are crucial analysis steps for any detection candidate events. Detailed models of the anticipated waveforms enable inference on several parameters, such as component masses, spins, sky location and distance, that are essential for new astrophysical studies of these sources. However, accurate measurements of these parameters and discrimination of models describing the underlying physics are complicated by artifacts in the data, uncertainties in the waveform models and in the calibration of the detectors. Here we report such measurements on a selection of simulated signals added either in hardware or software to the data collected by the two LIGO instruments and the Virgo detector during their most recent joint science run, including a "blind injection'' where the signal was not initially revealed to the collaboration. We exemplify the ability to extract information about the source physics on signals that cover the neutron-star and black-hole binary parameter space over the component mass range 1M(circle dot)-25M(circle dot) and the full range of spin parameters. The cases reported in this study provide a snapshot of the status of parameter estimation in preparation for the operation of advanced detectors.
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| 6. |
- Aasi, J., et al.
(författare)
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Search for gravitational waves from binary black hole inspiral, merger, and ringdown in LIGO-Virgo data from 2009-2010
- 2013
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 87:2
-
Tidskriftsartikel (refereegranskat)abstract
- We report a search for gravitational waves from the inspiral, merger and ringdown of binary black holes (BBH) with total mass between 25 and 100 solar masses, in data taken at the LIGO and Virgo observatories between July 7, 2009 and October 20, 2010. The maximum sensitive distance of the detectors over this period for a (20, 20)M-circle dot coalescence was 300 Mpc. No gravitational wave signals were found. We thus report upper limits on the astrophysical coalescence rates of BBH as a function of the component masses for nonspinning components, and also evaluate the dependence of the search sensitivity on component spins aligned with the orbital angular momentum. We find an upper limit at 90% confidence on the coalescence rate of BBH with nonspinning components of mass between 19 and 28M(circle dot) of 3:3 x 10(-7) mergers Mpc(-3) yr(-1).
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| 7. |
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| 8. |
- Abdalla, E., et al.
(författare)
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Cosmology intertwined : A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies
- 2022
-
Ingår i: Journal of High Energy Astrophysics. - : Elsevier BV. - 2214-4048 .- 2214-4056. ; 34, s. 49-211
-
Tidskriftsartikel (refereegranskat)abstract
- The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ωm, and the amplitude or rate of the growth of structure (σ8,fσ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions.
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| 9. |
- Alcorn, J, et al.
(författare)
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Basic instrumentation for Hall A at Jefferson Lab
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
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Tidskriftsartikel (refereegranskat)abstract
- The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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| 10. |
- Fages, A., et al.
(författare)
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Tracking Five Millennia of Horse Management with Extensive Ancient Genome Time Series
- 2019
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Ingår i: Cell. - : Elsevier BV. - 0092-8674. ; 177:6
-
Tidskriftsartikel (refereegranskat)abstract
- Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (>= 1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modem legacy of past equestrian civilisations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN "speed gene," only rose in popularity within the last millennium. Finally, the development of modem breeding impacted genetic diversity more dramatically than the previous millennia of human management.
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| 11. |
- Puckett, A. J. R., et al.
(författare)
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Final analysis of proton form factor ratio data at Q(2)=4.0, 4.8, and 5.6 GeV2
- 2012
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:4
-
Tidskriftsartikel (refereegranskat)abstract
- Precise measurements of the proton electromagnetic form factor ratio R = mu(p)G(E)(p)/G(M)(p) using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q(2) for Q(2) greater than or similar to 1 GeV2, in strong disagreement with previous extractions of R from cross-section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q(2) values in the range 3.5 GeV2 <= Q(2) <= 5.6 GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q(2) motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus, and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for R, improving the consistency of the polarization transfer data in the high-Q(2) region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis.
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| 12. |
- Balcou, P, et al.
(författare)
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High-order-harmonic generation: towards laser-induced phase-matching control and relativistic effects
- 2002
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 74:6, s. 509-515
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Tidskriftsartikel (refereegranskat)abstract
- We present a review of some recent results on high-order-harmonic generation, aiming at optimizing the photon flux to allow for future applications in extreme-ultra-violet non-linear optics. We first present new schemes to control phase matching of high harmonics in gases, by using the effect of the spatially varying atomic phase displayed by the high harmonics. An enhancement by a factor of 50 is observed in neon in conditions for which the gradient of the atomic dispersion balances the electronic dispersion. A new scheme to manipulate the laser field was demonstrated, and shown to improve phase matching. We then turn to high-harmonic generation by solid targets, and show that high harmonics generated by an intense 30-fs laser pulse remain collimated even at the threshold of the relativistic regime.
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| 13. |
- Alexandridi, C., et al.
(författare)
-
Attosecond photoionization dynamics in the vicinity of the Cooper minima in argon
- 2021
-
Ingår i: Physical Review Research. - 2643-1564. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Using a spectrally resolved electron interferometry technique, we measure photoionization time delays between the 3s and 3p subshells of argon over a large 34-eV energy range covering the Cooper minima in both subshells. The observed strong variations of the 3s−3p delay difference, including a sign change, are well reproduced by theoretical calculations using the two-photon two-color random-phase approximation with exchange. Strong shake-up channels lead to photoelectrons spectrally overlapping with those emitted from the 3s subshell. These channels need to be included in our analysis to reproduce the experimental data. Our measurements provide a benchmark for multielectronic theoretical models aiming at an accurate description of interchannel correlation.
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| 14. |
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| 15. |
- Arnold, C. L., et al.
(författare)
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Stabilized interferometric attosecond timing measurements
- 2013
-
Ingår i: CLEO : QELS_Fundamental Science, CLEO:QELS FS 2013 - QELS_Fundamental Science, CLEO:QELS FS 2013. - 9781557529725
-
Konferensbidrag (refereegranskat)abstract
- We perform interferometric attosecond timing measurements to study XUV photoionization in noble gases, to diagnose macroscopic phase-matching conditions in high-order harmonic generation, and to investigate single-photon double-ionization by detecting electron pairs in coincidence.
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| 16. |
- Arnold, C. L., et al.
(författare)
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The ELI-ALPS secondary sources : A getaway to scientific excellence
- 2013
-
Ingår i: 2013 Conference on Lasers and Electro-Optics, CLEO 2013. - 9781557529725 ; 2013
-
Konferensbidrag (refereegranskat)abstract
- The essence of ELI-ALPS, the laser driven secondary sources ranging from X-ray and X-UV to THz with duration as short as tens of attoseconds, are designed to be available for users from 2016.
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| 17. |
- Bastard, P, et al.
(författare)
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Vaccine breakthrough hypoxemic COVID-19 pneumonia in patients with auto-Abs neutralizing type I IFNs
- 2022
-
Ingår i: Science immunology. - : American Association for the Advancement of Science (AAAS). - 2470-9468. ; 78:7490, s. eabp8966-
-
Tidskriftsartikel (refereegranskat)abstract
- Life-threatening ‘breakthrough’ cases of critical COVID-19 are attributed to poor or waning antibody response to the SARS-CoV-2 vaccine in individuals already at risk. Pre-existing autoantibodies (auto-Abs) neutralizing type I IFNs underlie at least 15% of critical COVID-19 pneumonia cases in unvaccinated individuals; however, their contribution to hypoxemic breakthrough cases in vaccinated people remains unknown. Here, we studied a cohort of 48 individuals (age 20-86 years) who received 2 doses of an mRNA vaccine and developed a breakthrough infection with hypoxemic COVID-19 pneumonia 2 weeks to 4 months later. Antibody levels to the vaccine, neutralization of the virus, and auto-Abs to type I IFNs were measured in the plasma. Forty-two individuals had no known deficiency of B cell immunity and a normal antibody response to the vaccine. Among them, ten (24%) had auto-Abs neutralizing type I IFNs (aged 43-86 years). Eight of these ten patients had auto-Abs neutralizing both IFN-α2 and IFN-ω, while two neutralized IFN-ω only. No patient neutralized IFN-β. Seven neutralized 10 ng/mL of type I IFNs, and three 100 pg/mL only. Seven patients neutralized SARS-CoV-2 D614G and the Delta variant (B.1.617.2) efficiently, while one patient neutralized Delta slightly less efficiently. Two of the three patients neutralizing only 100 pg/mL of type I IFNs neutralized both D61G and Delta less efficiently. Despite two mRNA vaccine inoculations and the presence of circulating antibodies capable of neutralizing SARS-CoV-2, auto-Abs neutralizing type I IFNs may underlie a significant proportion of hypoxemic COVID-19 pneumonia cases, highlighting the importance of this particularly vulnerable population.
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| 18. |
- Busto, D., et al.
(författare)
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Time-frequency representation of autoionization dynamics in helium
- 2018
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:4
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Tidskriftsartikel (refereegranskat)abstract
- Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wave packet. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wave packets emitted via the sp2+ and sp3(+) resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time-frequency representations, we observe the build-up of the wave packets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels.
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| 19. |
- Gayou, O, et al.
(författare)
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Measurement of G(Ep)/G(Mp) in (e)over-right-arrowp -> e(p)over-right-arrow to Q(2)=5.6 GeV2
- 2002
-
Ingår i: Physical Review Letters. - 1079-7114. ; 88:9
-
Tidskriftsartikel (refereegranskat)abstract
- The ratio of the electric and magnetic form factors of the proton G(Ep)/G(Mp), which is an image of its charge and magnetization distributions, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic (e) over right arrowp --> e (p) over right arrow reaction. The new data presented span the range 3.5 < Q(2) < 5.6 GeV2 and are well described by a linear Q(2) fit. Also, the ratio rootQ(2) F-2p/F-1p reaches a constant value above Q(2) = 2 GeV2.
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| 20. |
- Gisselbrecht, M., et al.
(författare)
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Attosecond insight into electron correlation
- 2019
-
Ingår i: Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conference, CLEO/Europe-EQEC 2015. - 9781467374750
-
Konferensbidrag (refereegranskat)abstract
- Photoionization with a single photon is one of the fundamental processes in nature, in which one electron is ripped away from its atom. Traditionally studied in the energy domain, this process was believed to be instantaneous, but recent advances in the production of attosecond pulses (1 as 10−18 s) in the eXtreme UltraViolet (XUV) have renewed interest in understanding the temporal aspects of electron emission in atoms, molecules and the solid state [1–8]. We present here our progress in understanding the influence of electronic correlations on the attosecond photoionization dynamics.
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| 21. |
- Heyl, C. M., et al.
(författare)
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Noncollinear optical gating - A method for intra-cavity single attosecond pulse generation?
- 2019
-
Ingår i: Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conference, CLEO/Europe-EQEC 2015. - 9781467374750
-
Konferensbidrag (refereegranskat)abstract
- The process of high-order harmonic generation requires laser intensities around 1014 W/cm2, most easily reached with laser pulses of high energy, thus implicitly limiting the repetition rate of attosecond sources. A route towards multi-MHz attosecond sources relies on HHG inside a passive enhancement cavity [1]. Although successfully demonstrated for attosecond pulse trains, the generation of single attosecond pulses (SAPs) inside a cavity remains an unsolved challenge, mainly limited by dispersion management and out-coupling problems. We recently proposed a new gating concept for SAP generation [2], noncollinear optical gating (NOG) which has the potential to facilitate SAP gating and efficient out-coupling at once. Similar to the recently introduced attosecond lighthouse [3] NOG employs attosecond angular streaking [4] and combines this concept with noncollinear HHG, proposed earlier [5] as out-coupling method for intra cavity HHG.
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| 22. |
- Isinger, M., et al.
(författare)
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Photoionization in the time and frequency domain
- 2017
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 358:6365, s. 893-6
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Tidskriftsartikel (refereegranskat)abstract
- Ultrafast processes in matter, such as the electron emission following light absorption, can now be studied using ultrashort light pulses of attosecond duration (10−18 s) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40 eV energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake-up, in which a second electron is left in an excited state, and obtain excellent agreement with theoretical calculations, thereby solving a puzzle raised by 7-year-old measurements.
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| 23. |
- Laurell, H., et al.
(författare)
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Continuous-variable quantum state tomography of photoelectrons
- 2022
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Ingår i: Physical Review Research. - 2643-1564. ; 4:3
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a continuous variable quantum state tomography protocol of electrons which result from the ionization of atoms or molecules by the absorption of extreme ultraviolet light pulses. Our protocol is benchmarked against a direct calculation of the quantum state of photoelectrons ejected from helium and argon in the vicinity of a Fano resonance. In the latter case, we furthermore distill ion-photoelectron entanglement due to spin-orbit splitting. This opens routes toward the investigation of quantum coherence and entanglement properties on the ultrafast timescale.
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| 24. |
- Lorek, Eleonora, et al.
(författare)
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High-Order Harmonic Generation and Plasmonics
- 2015
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Ingår i: Nano-Structures for Optics and Photonics : Optical Strategies for Enhancing Sensing, Imaging, Communication and Energy Conversion - Optical Strategies for Enhancing Sensing, Imaging, Communication and Energy Conversion. - Dordrecht : Springer Netherlands. - 9789401791328 - 9789401791335 ; , s. 531-531
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Bokkapitel (refereegranskat)abstract
- Attosecond pulses allow for imaging of very fast processes, like electron dynamics. Stockman et al. suggested to use these pulses in connection with a Photoemission electron microscope (PEEM) to study the ultrafast dynamics of plasmons (Stockman et al. Nat Photonics 1:539–544, 2007). For efficient plasmon studies, the repetition rate of the attosecond pulses used needs to be higher than a few kHz (Mikkelsen et al. Rev Sci Instrum 80:123703, 2009). Attosecond pulses are produced in a process called high-order harmonic generation (HHG) (Paul et al. Science 292(5522):1689–1692, 2001; Ferray et al. J Phys B At Mol Opt Phys 21:L31–L35, 1988). In HHG, a strong laser field allows an electron to tunnel out, get accelerated and recombine with a high kinetic energy resulting in extreme ultraviolet attosecond pulses. The large intensity needed to drive the process normally limits the repetition rate of the laser to a few kHz. Using a tight focusing scheme (Heyl et al. Phys Rev Lett 107:033903, 2011; Vernaleken et al. Opt Lett 36:3428–3430, 2011), we, however, generate harmonics at a repetition rate of 200 kHz, both with a commercial turn-key laser and with an advanced laser system. Suitable nanostructures for a strong field enhancement are produced in-house and the field enhancement is studied with PEEM in a non-time resolved manner. With high-order harmonics produced at a high repetition rate, we hope to be able to follow also the ultrafast dynamics of plasmons in these structures (Mårsell et al. Ann der Phys 525:162–170, 2013).
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| 25. |
- Merdji, H., et al.
(författare)
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Coherence properties of high-order harmonics : Application to high-density laser-plasma diagnostic
- 2000
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 18:3, s. 495-502
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Tidskriftsartikel (refereegranskat)abstract
- We present two interferometry schemes in the extreme ultraviolet, based on either the wave-front division of a unique harmonic beam (1st scheme) or two spatially separated, phase-locked harmonic sources (2nd scheme). In the first scheme using a Fresnel bimirror interferometer, we measure the degree of spatial coherence of the 13 th harmonic generated in xenon, as a function of different parameters. A high degree of coherence, larger than 0.5, is found for the best conditions in almost the full section of the beam. Then, we demonstrate that the second scheme can be used for interferometry measurements with an ultrahigh time resolution. The 11th harmonic is used to study the spatial variation of the electron density of a laser-produced plasma. Electronic densities higher than 2.10 20 cm -3 are measured.
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| 26. |
- Zhong, S., et al.
(författare)
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Probing photoionization dynamics by high-spectral-resolution attosecond spectroscopy
- 2018
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Ingår i: Optics InfoBase Conference Papers. - 9781557528209 ; Part F115-LS 2018
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Konferensbidrag (refereegranskat)abstract
- Photoionization time delays are measured with two-color (XUV+IR) interferometric techniques. The combination of attosecond temporal resolution and high spectral resolution from narrowband harmonics allows the study of ultrafast dynamics in both time and frequency domain.
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| 27. |
- Antoine, P, et al.
(författare)
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Generation of attosecond pulses in macroscopic media
- 1997
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 56:6, s. 4960-4969
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Tidskriftsartikel (refereegranskat)abstract
- We describe theoretically the generation of ultrashort (subfemtosecond) pulses using high-order harmonics of a laser pulse with a time-dependent degree of ellipticity. The single-atom response is calculated by using a low-frequency strong-field approximation. Propagation effects are taken into account using a method going beyond the slowly varying envelope approximation. Propagation modifies significantly the results obtained in the single-atom response and, in certain conditions, makes the generation of one attosecond pulse possible. We discuss prospects for the observation of these ultrashort pulses. [S1050-2947(97)09411-0].
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| 28. |
- Balcou, P, et al.
(författare)
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High-order harmonic generation processes in classical and quantum anharmonic oscillators
- 1996
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 53:5, s. 3456-3468
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical study of high-order harmonic generation by a slowly driven ''Duffing'' anharmonic oscillator. The power spectra are shown to display a plateau of high harmonics, which ends up with a sharp cutoff. The classical dynamics is analyzed with the adiabatic invariance theorem, which yields a simple interpretation to this characteristic behavior. We compare with the quantum case by solving numerically the time-dependent Schrodinger equation, and outline the similarity between classical damping and quantum-mechanical ionization processes. This allows us, in particular, to interpret the existence of intrinsic phases between high harmonics and the driving field. We further discuss the implication of these relaxation processes on the coherence of high harmonics, as well as the existence of interference processes yielding quasiresonant structures in intensity dependences.
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| 29. |
- Bengtsson, S., et al.
(författare)
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Space–time control of free induction decay in the extreme ultraviolet
- 2017
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 11:4, s. 252-258
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Tidskriftsartikel (refereegranskat)abstract
- Ultrafast extreme-ultraviolet (XUV) and X-ray sources are revolutionizing our ability to follow femtosecond processes with ångström-scale resolution. The next frontier is to simultaneously control the direction, duration and timing of such radiation. Here, we demonstrate a fully functional opto-optical modulator for XUV light, similar to modulators available at infrared (IR) and visible wavelengths. It works by using an IR pulse to control the spatial and spectral phase of the free induction decay that results from using attosecond pulses to excite a gas. The modulator allows us to send the XUV light in a direction of our choosing at a time of our choosing. The inherent synchronization of the XUV emission to the control pulse will allow laser-pump/X-ray probe experiments with sub-femtosecond time resolution.
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| 30. |
- Busto, D., et al.
(författare)
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Fano's propensity rule in angle-resolved attosecond interferometry
- 2020. - 7
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Ingår i: Attosecond Physics. - : IOP Publishing. - 1742-6588. ; 1412
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Konferensbidrag (refereegranskat)abstract
- Above-threshold ionization is a corner stone of attsecond science. In this work we extend Fano's propensity rule to two-photon above-threshold ionization and show that the asymmetry between absorption and emission of the second photon predicted by this propensity rule has strong implications for angle-resolved pump-probe experiments and in particular for attosecond photoelectron interferometry.
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| 31. |
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| 32. |
- Descamps, D, et al.
(författare)
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Extreme ultraviolet interferometry measurements with high-order harmonics
- 2000
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Ingår i: Optics Letters. - 0146-9592. ; 25:2, s. 135-137
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that high-order harmonics generated by short, intense laser pulses in gases provide an interesting radiation source for extreme ultraviolet interferometry, since they are tunable, coherent, of short pulse duration, and simple to manipulate. Harmonics from the 9th to the 15th are used to measure the thickness of an aluminum layer. The 11th harmonic is used to determine the spatial distribution of the electron density of a plasma produced by a 300-ps laser. Electronic densities higher than 2-10(20) electrons/cm(3) are measured. (C) 2000 Optical Society of America. OCIS codes: 190.0190, 190.4160, 190.7110, 120.3180, 140.7240, 350.4500.
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| 33. |
- Descamps, D, et al.
(författare)
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Two- and three-photon ionization of rare gases using femtosecond harmonic pulses generated in a gas medium
- 2001
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 64:3
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Tidskriftsartikel (refereegranskat)abstract
- The fifth harmonic of a 60-fs 10-Hz terawatt titanium:sapphire laser generated in Xe gas is used to ionize Xe and Kr atoms by nonresonant two-photon absorption and At atoms through a quasiresonant three-photon process. At relatively low harmonic yields, the variation of the number of Kr and Xe ions with the number of harmonic photons is quadratic. At high harmonic yields, it deviates from a quadratic behavior, which we attribute to the influence of ionization in the harmonic process distorting the harmonic wave front. The two-photon ionization cross sections in Xe and Kr at 160 nm are found to be comparable.
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| 34. |
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| 35. |
- Guenot, Diego, et al.
(författare)
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Probing electron correlation on the attosecond time scale
- 2014
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Ingår i: High Intensity Lasers and High Field Phenomena, HILAS 2014. - 9781557529954
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Konferensbidrag (refereegranskat)abstract
- We present experimental measurements and theoretical calculations of single and double ionization time delays in various noble gases using an interferometric method. The measured delays allow us to extract information on the electron correlation.
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| 36. |
- Hergott, JF, et al.
(författare)
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XUV interferometry using high-order harmonics: Application to plasma diagnostics
- 2001
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 19:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present and compare the two different XUV interferometric techniques using high-order harmonics that have been developed so far. The first scheme is based on the interference between two spatially separated phase-locked harmonic sources while the second uses two temporally separated harmonic sources. These techniques have been applied to plasma diagnostics in feasibility experiments where electron densities up to a few 1020 e[minus sign/cm3 have been measured with a temporal resolution of 200 fs. We present the main characteristics of each technique and discuss their respective potentials and limitations.
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| 37. |
- Hoff, D., et al.
(författare)
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Direct CEP Stabilization of a high-repetition rate, few-cycle OPCPA chain with a single feedback loop, employing a Stereo-ATI
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
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Konferensbidrag (refereegranskat)abstract
- Today's Carrier-Envelope Phase (CEP) stabilizations of mode-locked oscillators widely used in attosecond science and frequency metrology rely on octave spanning frequency combs and the detection of beating between the blue end and the frequency doubled red end of the same spectrum. This technique was established by the seminal works of Hänsch and co-workers [1], demonstrating the stabilization of optical frequencies from such a frequency comb by transferring the slippage of the CEP (or carrier-envelope offset frequency) into a detectable radio frequency by f-2f interferometry. The requirement of an octave spanning spectrum means that usually some kind of super-continuum generation is involved, which, in practice often is a fragile scheme since wide band oscillators are very prone to instabilities and noise.
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| 38. |
- Hoff, D., et al.
(författare)
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Quantum Beat Spectroscopy of Helium Photoelectrons
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
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Konferensbidrag (refereegranskat)abstract
- The availability of broadband extreme ultraviolet light sources allows for investigation of electron wave-packets from high lying bound states in atoms [1,2]. The dynamics of these states can be mapped out in the ionization continuum with an overlapping infrared field, which may also uncover new, light induced, dressed states [3]. Here, we carry out a complete characterization of these electron wave-packets using a small number of attosecond pulses.
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| 39. |
- Isinger, M., et al.
(författare)
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Accuracy and precision of the RABBIT technique
- 2019
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Ingår i: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Science. - : The Royal Society. - 1364-503X .- 1471-2962. ; 377:2145
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Tidskriftsartikel (refereegranskat)abstract
- One of the most ubiquitous techniques within attosecond science is the so-called reconstruction of attosecond beating by interference of two-photon transitions (RABBIT). Originally proposed for the characterization of attosecond pulses, it has been successfully applied to the accurate determination of time delays in photoemission. Here, we examine in detail, using numerical simulations, the effect of the spatial and temporal properties of the light fields and of the experimental procedure on the accuracy of the method. This allows us to identify the necessary conditions to achieve the best temporal precision in RABBIT measurements. This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'.
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| 40. |
- Johansson, Allan, et al.
(författare)
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Two-color pump-probe experiments in helium using high-order harmonics
- 2003
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 22:1, s. 3-11
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Tidskriftsartikel (refereegranskat)abstract
- A pump-probe technique has been applied for measuring the lifetimes and absolute photoionization cross-sections of excited He states. The 1s2p P-1 and 1s3p P-1 states of He are excited by using the 13th and the 14th harmonic, respectively, of a tunable 70 ps dye laser generated in a Kr gas jet. The states are ionized after a varying time delay, by absorption of probe photons with energies between 1.6 and 4.5 eV. Lifetimes of tau(1s2p) = 0.57 ns and tau(1s3p) = 1.76 ns are determined with a precision of about 15%. A significant enhancement of the number of ions present in the lifetime curves at zero time delay for pressures above 6 x 10(-5) mbar is attributed to direct two-photon ionization of He in combination with AC Stark broadening of the excited state and absorption of the XUV light in the medium. Absolute photoionization cross-sections from the He 1s2p P-1 and He 1s3p P-1 states in the threshold region are determined by measuring the saturation of the ionization process with a precision of similar to 25%. In addition, the variation of the relative orientation between the polarization vectors of the pump and probe beams enables the determination of partial photoionization cross-sections.
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| 41. |
- Lappas, D. G, et al.
(författare)
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Generation of attosecond xuv pulses in strong laser-atom interactions
- 1998
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 58:5, s. 4140-4146
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Tidskriftsartikel (refereegranskat)abstract
- The generation of radiation pulses that can be as short as 120 attoseconds is demonstrated theoretically. We have employed a two-dimensional exact solution of the Schrodinger equation that allows for arbitrary laser ellipticity. By manipulating the laser ellipticity in time, it is shown that one can control the wave-packet dynamics of the ejected atomic electron. The nonlinear interaction of the electron with the atomic core can thus be restricted to extremely short times. Photon energies up to 160 eV are generated. It is also shown that with a higher laser frequency, even shorter pulses can be produced. [S1050-2947(98)02211-2].
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| 42. |
- L'Huillier, Anne, et al.
(författare)
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Applications of high-order harmonics
- 2003
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 26:1, s. 91-98
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Tidskriftsartikel (refereegranskat)abstract
- We review applications of high-order harmonic generation in different fields of physics, from spectroscopic studies of atoms and molecules, to interferometry and plasma diagnostics and nonlinear optics.
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| 43. |
- L'Huillier, Anne, et al.
(författare)
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High-order Harmonics - A Coherent Source In the Xuv Range
- 1995
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Ingår i: Journal of Nonlinear Optical Physics & Materials. - 0218-1991. ; 4:3, s. 647-665
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Tidskriftsartikel (refereegranskat)abstract
- We review the main results concerning high-order generation processes from the point of view of a potential user of this new source of XUV radiation. The perspectives for optimizing the source, both in efficiency and in spectral range, its characteristics and in particular, its coherence properties, are discussed. Finally, we describe two experiments, which demonstrate the usefulness of the harmonics as a short-pulse, coherent source in the XUV domain.
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| 44. |
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| 45. |
- Makos, I, et al.
(författare)
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Α 10-gigawatt attosecond source for non-linear XUV optics and XUV-pump-XUV-probe studies
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The quantum mechanical motion of electrons and nuclei in systems spatially confined to the molecular dimensions occurs on the sub-femtosecond to the femtosecond timescales respectively. Consequently, the study of ultrafast electronic and, in specific cases, nuclear dynamics requires the availability of light pulses with attosecond (asec) duration and of sufficient intensity to induce two-photon processes, essential for probing the intrinsic system dynamics. The majority of atoms, molecules and solids absorb in the extreme-ultraviolet (XUV) spectral region, in which the synthesis of the required attosecond pulses is feasible. Therefore, the XUV spectral region optimally serves the study of such ultrafast phenomena. Here, we present a detailed review of the first 10-GW class XUV attosecond source based on laser driven high harmonic generation in rare gases. The pulse energy of this source largely exceeds other laser driven attosecond sources and is comparable to the pulse energy of femtosecond Free-Electron-Laser (FEL) XUV sources. The measured pulse duration in the attosecond pulse train is 650 ± 80 asec. The uniqueness of the combined high intensity and short pulse duration of the source is evidenced in non-linear XUV-optics experiments. It further advances the implementation of XUV-pump-XUV-probe experiments and enables the investigation of strong field effects in the XUV spectral region.
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| 46. |
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| 47. |
- Nandi, S., et al.
(författare)
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Attosecond timing of electron emission from a molecular shape resonance
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:31
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Tidskriftsartikel (refereegranskat)abstract
- Shape resonances in physics and chemistry arise from the spatial confinement of a particle by a potential barrier. In molecular photoionization, these barriers prevent the electron from escaping instantaneously, so that nuclei may move and modify the potential, thereby affecting the ionization process. By using an attosecond two-color interferometric approach in combination with high spectral resolution, we have captured the changes induced by the nuclear motion on the centrifugal barrier that sustains the well-known shape resonance in valence-ionized N-2. We show that despite the nuclear motion altering the bond length by only 2%, which leads to tiny changes in the potential barrier, the corresponding change in the ionization time can be as large as 200 attoseconds. This result poses limits to the concept of instantaneous electronic transitions in molecules, which is at the basis of the Franck-Condon principle of molecular spectroscopy.
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| 48. |
- Neoričić, L., et al.
(författare)
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Resonant two-photon ionization of helium atoms studied by attosecond interferometry
- 2022
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Ingår i: Frontiers in Physics. - : Frontiers Media SA. - 2296-424X. ; 10
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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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| 49. |
- Norin, Johan, et al.
(författare)
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Design of an extreme-ultraviolet monochromator free from temporal stretching
- 2004
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Ingår i: Applied Optics. - 2155-3165. ; 43:5, s. 1072-1081
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Tidskriftsartikel (refereegranskat)abstract
- High-order harmonic generation in gases by use of femtosecond lasers is a source of ultrashort pulses in the extreme-ultraviolet (XUV). For many applications it is necessary to select radiation of only one specific harmonic order without affecting the duration of the ultrashort pulse. A three-grating monochromator that meets this demand has been designed and modeled by ray tracing as well as by wave-optical simulations. The only remaining temporal stretching of an XUV pulse is due to distortion of the pulse front on the gratings and is predicted to be similar to1 fs. The design has been successfully tested in the near infrared. Finally, the monochromator is also capable of eliminating any existing linear chirp in the harmonic pulses, thus compressing them to shorter durations. (C) 2004 Optical Society of America.
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| 50. |
- Roos, L, et al.
(författare)
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Controlling phase matching of high-order harmonic generation by manipulating the fundamental field
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:6, s. 5010-5018
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Tidskriftsartikel (refereegranskat)abstract
- We study experimentally how to control and improve phase matching of high-order harmonic generation. We use a birefringent lens and a birefringent compensator to obtain a fundamental laser pulse (150 fs, 800 nm, similar to 4 mJ) With two foci Separated by 6.2 mm along the propagation axis and with a controllable phase delay between the polarizations along the optic axes of the birefringent optical components. This enables us to enhance the high-order harmonic conversion efficiency for the high-order harmonics in neon to 3 x 10(-8), a factor of 4 higher compared to a single-focus setup in similar conditions. The enhancement is achieved by improving the phase matching and at the same time maintaining a high intensity in a large generating volume. [S1050-2947(99)04512-6].
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