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Sökning: WFRF:(Dahlström Marcus)

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1.
  • Busto, David, et al. (författare)
  • Fano's Propensity Rule in Angle-Resolved Attosecond Pump-Probe Photoionization
  • 2019
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 123:13
  • Tidskriftsartikel (refereegranskat)abstract
    • In a seminal article, Fano predicts that absorption of light occurs preferably with increase of angular momentum. We generalize Fano's propensity rule to laser-assisted photoionization, consisting of absorption of an extreme-ultraviolet photon followed by absorption or emission of an infrared photon. The predicted asymmetry between absorption and emission leads to incomplete quantum interference in attosecond photoelectron interferometry. It explains both the angular dependence of the photoionization time delays and the delay dependence of the photoelectron angular distributions. Our theory is verified by experimental results in Ar in the 20-40 eV range.
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2.
  • Petersson, C. L.M., et al. (författare)
  • Anisotropic photoemission time delays close to a Fano resonance
  • 2018
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • Electron correlation and multielectron effects are fundamental interactions that govern many physical and chemical processes in atomic, molecular and solid state systems. The process of autoionization, induced by resonant excitation of electrons into discrete states present in the spectral continuum of atomic and molecular targets, is mediated by electron correlation. Here we investigate the attosecond photoemission dynamics in argon in the 20-40 eV spectral range, in the vicinity of the 3s(-1)np autoionizing resonances. We present measurements of the differential photoionization cross section and extract energy and angle-dependent atomic time delays with an attosecond interferometric method. With the support of a theoretical model, we are able to attribute a large part of the measured time delay anisotropy to the presence of autoionizing resonances, which not only distort the phase of the emitted photoelectron wave packet but also introduce an angular dependence.
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3.
  • Zhong, Shiyang, et al. (författare)
  • Attosecond electron–spin dynamics in Xe 4d photoionization
  • 2020
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The photoionization of xenon atoms in the 70–100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe+ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past, using in particular synchrotron radiation, but without access to real-time dynamics. Here, we study the dynamics of Xe 4d photoionization on its natural time scale combining attosecond interferometry and coincidence spectroscopy. A time-frequency analysis of the involved transitions allows us to identify two interfering ionization mechanisms: the broad giant dipole resonance with a fast decay time less than 50 as, and a narrow resonance at threshold induced by spin-flip transitions, with much longer decay times of several hundred as. Our results provide insight into the complex electron-spin dynamics of photo-induced phenomena.
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4.
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5.
  • Bertolino, Mattias, et al. (författare)
  • Multiphoton interaction phase shifts in attosecond science
  • 2021
  • Ingår i: Physical Review Research. - 2643-1564. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Ab initio simulations of a range of interferometric experiments are used to identify a strong dependence on multiphoton phase shifts in above-threshold ionization (ATI). A simple rule of thumb for interaction phase shifts is derived to explain both the conservation of photoelectron yield and its absolute CEP dependence. For instance, it is found that interferometric (ATI) experiments are shifted by π/4 relative to RABBIT experiments, and that there is no RABBIT term in a laser-assisted photoionization experiment with odd and even harmonics. Thus, our work helps to resolve the issues of interpretation of quantum dynamics in attosecond and free-electron laser sciences.
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6.
  • Bertolino, Mattias, et al. (författare)
  • Propensity rules and interference effects in laser-Assisted photoionization of helium and neon
  • 2020
  • Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:14
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the angle-resolved photoelectron spectra from laser-Assisted photoionization for helium and neon atoms using an ab initio method based on time-dependent surface flux and configuration interaction singles. We find that the shape of the distributions can be interpreted using a propensity rule, an intrinsic difference in the absorption and the emission processes, as well as interference effects between multiple paths to the final angular momentum state. The difference between absorption and emission is hidden in the first sideband in neon due to the multiple competing m channels, while in the second sideband a qualitative difference between absorption and emission is observed. In the m-resolved case, a clear difference is observed already in the first sideband, as exemplified in helium and m-resolved neon.
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7.
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8.
  • Bertolino, Mattias, et al. (författare)
  • Thomas-Reiche-Kuhn correction for truncated configuration-interaction spaces : Case of laser-assisted dynamical interference
  • 2022
  • Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 106:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The Thomas-Reiche-Kuhn sum rule is used to form an effective potential that is added to the time-dependent configuration-interaction singles (TDCIS) equations of motion in velocity gauge. The purpose of the effective potential is to include virtual coupling from singles to doubles, which is required for size-consistent velocity-gauge TDCIS results. The proposed method is compared to length-gauge TDCIS results for laser-assisted photoionization. Finally, a dynamical interference effect controlled by two-color fields is predicted for atomic targets. 
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9.
  • Braunschweig, Frieder, et al. (författare)
  • New York Heart Association functional class, QRS duration, and survival in heart failure with reduced ejection fraction : implications for cardiac resychronization therapy.
  • 2017
  • Ingår i: European Journal of Heart Failure. - : Wiley-Blackwell. - 1388-9842 .- 1879-0844. ; 19:3, s. 366-376
  • Tidskriftsartikel (refereegranskat)abstract
    • AIMS: Symptom severity assessed by NYHA functional class and QRS duration are essential criteria for selection of heart failure (HF) patients for CRT. This study assessed the relationship between NYHA class, QRS duration, and survival in a nationwide HF registry.METHODS AND RESULTS: We studied 13 423 patients with HF in NYHA class II-IV and LVEF <40% in the Swedish Heart Failure Registry. Survival was followed via the Swedish Population Registry. Of 12 534 patients without CRT (age 71 ± 12 years, 29% women), 51% and 49% were in NYHA class II and III-IV, respectively. Patients in NYHA class II compared with class III-IV were younger (69 vs. 73 years), and had a better systolic function (49% vs. 58% with LVEF <30%), P <0.001 for all, and a favourable co-morbidity profile. QRS duration was 116 ± 29 ms in NYHA class II and 119 ± 29 ms in NYHA class III-IV with QRS ≥120 ms found in 37% vs. 44%, and an LBBB in 23% vs. 28% (P < 0.001 for all). Upon multivariable Cox regression adjusting for 40 clinically relevant variables, mortality risk was higher in NYHA class III-IV vs. class II, with a hazard ratio (HR) of 1.31, 95% confidence interval (CI) 1.23-1.40. Mortality was also higher with QRS prolongation ≥120 ms vs. narrow QRS. The HR in NYHA class II patients with non-LBBB was 1.19 (95% CI 1.05 - 1.36) and in those with LBBB it was 1.16 (95% CI 1.03-1.41). The corresponding HRs in NYHA class III-IV were 1.33 (95% CI 1.21-1.47) and 1.12 (95% CI 1.02-1.22). There was no significant interaction between the effects of NYHA class and QRS duration or morphology on mortality. Applying different scenarios to estimate guideline adherence, fewer patients with NYHA class II (range 14.4-42.6%) compared with NYHA class III-IV (18.0-45.4%) had received a CRT device when indicated.CONCLUSIONS: In HF with reduced LVEF, QRS prolongation is common and independently linked to worse survival. The increase in mortality risk associated with QRS prolongation of both LBBB and non-LBBB morphology is similar in NYHA class II and III-IV.
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10.
  • Brizuela, Fernando, et al. (författare)
  • Efficient high order harmonic generation boosted by below threshold harmonics
  • 2013
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3
  • Tidskriftsartikel (refereegranskat)abstract
    • High-order harmonic generation (HHG) in gases has been established as an important technique for the generation of coherent extreme ultraviolet (XUV) pulses at ultrashort time scales. Its main drawback, however, is the low conversion efficiency, setting limits for many applications, such as ultrafast coherent imaging, nonlinear processes in the XUV range, or seeded free electron lasers. Here we introduce a novel scheme based on using below-threshold harmonics, generated in a seeding cell, to boost the HHG process in a generation cell, placed further downstream in the focused laser beam. By modifying the fundamental driving field, these low-order harmonics alter the ionization step of the nonlinear HHG process. Our dual-cell scheme enhances the conversion efficiency of HHG, opening the path for the realization of robust intense attosecond XUV sources.
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11.
  • Carette, Thomas, et al. (författare)
  • Multiconfigurational Hartree-Fock close-coupling ansatz : Application to the argon photoionization cross section and delays
  • 2013
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 87:2, s. 023420-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a robust, ab initio method for addressing atom-light interactions and apply it to photoionization of argon. We use a close-coupling ansatz constructed on a multiconfigurational Hartree-Fock description of localized states and B-spline expansions of the electron radial wave functions. In this implementation, the general many-electron problem can be tackled thanks to the use of the ATSP2K libraries [C. Froese Fischer et al., Comput. Phys. Commun. 176, 559 (2007)]. In the present contribution, we combine this method with exterior complex scaling, thereby allowing for the computation of the complex partial amplitudes that encode the whole dynamics of the photoionization process. The method is validated on the 3s3p(6)np series of resonances converging to the 3s extraction. Then, it is used for computing the energy dependent differential atomic delay between 3p and 3s photoemission, and agreement is found with the measurements of Guenot et al. [Phys. Rev. A 85, 053424 (2012)]. The effect of the presence of resonances in the one-photon spectrum on photoionization delay measurements is studied. DOI: 10.1103/PhysRevA.87.023420
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12.
  • Carlström, Stefanos, et al. (författare)
  • Control of spin polarization through recollisions
  • 2023
  • Ingår i: Physical Review A. - 2469-9926. ; 108:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Using only linearly polarized light, we study the possibility of generating spin-polarized photoelectrons from xenon atoms. No net spin polarization is possible, since the xenon ground state is spinless, but when the photoelectrons are measured in coincidence with the residual ion, spin polarization emerges. Furthermore, we show that ultrafast dynamics of the recolliding photoelectrons contribute to an apparent flipping of the spin of the photoelectron, a process that has been completely neglected so far in all analyses of recollision-based processes. We link this phenomenon to the "spin-orbit clock"of the remaining ion. These effects arise already in dipole approximation.
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13.
  • Carlström, Stefanos, et al. (författare)
  • General time-dependent configuration-interaction singles. II. Atomic case
  • 2022
  • Ingår i: Physical Review A. - 2469-9926. ; 106:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a specialization of the grid-based implementation of the time-dependent configuration-interaction singles described in the preceding paper [S. Carlström et al., preceding paper, Phys. Rev. A 106, 043104 (2022)]10.1103/PhysRevA.106.043104. to the case of spherical symmetry. We describe the intricate time propagator in detail and conclude with a few example calculations. Among these, of note are high-resolution photoelectron spectra in the vicinity of the Fano resonances in photoionization of neon and spin-polarized photoelectrons from xenon, in agreement with recent experiments.
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14.
  • Carlström, Stefanos, et al. (författare)
  • Rydberg atomic antenna in strongly driven multielectron atoms
  • 2022
  • Ingår i: Physical Review A. - 2469-9926. ; 106:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the role of intermediate excitations of Rydberg states as an example of Kuchiev's "atomic antenna"in above-threshold ionization of xenon, in particular their effect on the coherence between the spin-orbit-split states of the ion. We focus on the case of a laser frequency close to resonant with the spin-orbit splitting, where a symmetry (parity) argument would preclude any coherence being directly generated by strong-field ionization. Using ab initio simulations of coupled multielectron spin-orbit dynamics in strong laser fields, we show how field-driven rescattering of the trapped Rydberg electrons introduces efficient coupling between the spin-orbit-split channels, leading to substantial coherences, exceeding 10% for some photon energies.
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15.
  • Dahlström, Jan Marcus, et al. (författare)
  • Attosecond transient absorption of a bound wave packet coupled to a smooth continuum
  • 2017
  • Ingår i: Journal of Optics. - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 19:11
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the possibility of using transient absorption of a coherent bound electron wave packet in hydrogen as an attosecond pulse characterization technique. In a recent work, we have shown that photoionization of such a coherent bound electron wave packet opens up for pulse characterization with unprecedented temporal accuracy-independent of the atomic structure-with maximal photoemission at all kinetic energies given a wave packet with zero relative phase (Pabst and Dahlstrom Phys. Rev. A 94 13411 (2016)). Here, we perform numerical propagation of the time-dependent Schrodinger equation and analytical calculations based on perturbation theory to show that the energy-resolved maximal absorption of photons from the attosecond pulse does not uniquely occur at a zero relative phase of the initial wave packet. Instead, maximal absorption occurs at different relative wave packet phases, distributed as a non-monotonous function with a smooth -pi/2 shift across the central photon energy (given a Fourier-limited Gaussian pulse). Similar results are also found in helium. Our finding is surprising, because it implies that the energy-resolved photoelectrons are not mapped one-to-one with the energy-resolved absorbed photons of the attosecond pulse.
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16.
  • Dahlström, J. Marcus, et al. (författare)
  • Diagrammatic approach to attosecond delays in photoionization
  • 2012
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 86:6, s. 061402-
  • Tidskriftsartikel (refereegranskat)abstract
    • We study laser-assisted photoionization by attosecond pulses using a time-independent formalism based on diagrammatic many-body perturbation theory. Our aim is to provide an ab initio route to the delays for this above-threshold ionization process, which is essential for a quantitative understanding of attosecond metrology. We present correction curves for characterization schemes of attosecond pulses, such as streaking, that account for the delayed atomic response in ionization from neon and argon. We also verify that photoelectron delays from many-electron atoms can be measured using similar schemes if, instead, the so-called continuum-continuum delay is subtracted. Our method is general and it can be extended also to more complex systems and additional correlation effects can be introduced systematically. DOI: 10.1103/PhysRevA.86.061402
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17.
  • Dahlström, J. Marcus, et al. (författare)
  • Introduction to attosecond delays in photoionization
  • 2012
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 45:18, s. 183001-
  • Tidskriftsartikel (refereegranskat)abstract
    • This tutorial presents an introduction to the interaction of light and matter on the attosecond timescale. Our aim is to detail the theoretical description of ultra-short time delays and to relate these to the phase of extreme ultraviolet (XUV) light pulses and to the asymptotic phaseshifts of photoelectron wave packets. Special emphasis is laid on time-delay experiments, where attosecond XUV pulses are used to photoionize target atoms at well-defined times, followed by a probing process in real time by a phase-locked, infrared laser field. In this way, the laser field serves as a 'clock' to monitor the ionization event, but the observable delays do not correspond directly to the delay associated with single-photon ionization. Instead, a significant part of the observed delay originates from a measurement induced process, which obscures the single-photon ionization dynamics. This artefact is traced back to a phaseshift of the above-threshold ionization transition matrix element, which we call the continuum-continuum phase. It arises due to the laser-stimulated transitions between Coulomb continuum states. As we shall show here, these measurement-induced effects can be separated from the single-photon ionization process, using analytical expressions of universal character, so that eventually the attosecond time delays in photoionization can be accessed.
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18.
  • Dahlström, J. Marcus, et al. (författare)
  • Photoionization Time Delays
  • 2016
  • Ingår i: Ultrafast Dynamics Driven by Intense Light Pulses. - Cham : Springer. - 9783319201726 - 9783319201733 ; , s. 177-202
  • Bokkapitel (refereegranskat)abstract
    • The material presented in this chapter is based on important advances realized in attophysics which make feasible to follow the motion of electrons in atoms and molecules with attosecond-level time resolution. In this context, time-delays have been recently determined in the process of photoionization by extreme-ultra- violet (XUV) pulses and the question of the significance of these measured delays arises. As we shall outline here, numerical experiments show that they are intimately related to the structure of the ionized species' continuous spectrum. Another point addressed here is that, in experiments, the measurements have the common characteristic to be performed in the presence of an auxiliary infra-red (IR) field, used to clock the timing of the process. This implies to adapt the theory treatment to handle such two-color photoionization processes. We review a systematic analysis of these features that are characteristic of this class of electronic transitions, when viewed in the time domain.
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19.
  • Dahlström, Jan Marcus, et al. (författare)
  • Pulse analysis by delayed absorption from a coherently excited atom
  • 2019
  • Ingår i: Apl Photonics. - : AIP Publishing. - 2378-0967. ; 4:1
  • Tidskriftsartikel (refereegranskat)abstract
    • In this tutorial, we provide a short review of attosecond pulse characterization techniques and a pedagogical account of a recently proposed method called Pulse Analysis by Delayed Absorption (PANDA) [S. Pabst and J. M. Dahlstrom, Phys. Rev. A 94, 013411 (2016)]. We discuss possible implementations of PANDA in alkali atoms using either principal quantum number wave packets or spin-orbit wave packets. The main merit of the PANDA method is that it can be used as a pulse characterization method that is free from atomic latency effects, such as scattering phase shifts and long-lived atomic resonances. Finally, we propose that combining the PANDA method with angle-resolved photoelectron detection should allow for experimental measurements of attosecond delays in photoionization from bound wave packets on the order of tens of attoseconds.
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20.
  • Dahlström, J. Marcus, et al. (författare)
  • Study of attosecond delays using perturbation diagrams and exterior complex scaling
  • 2014
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 47:12, s. 124012-
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange. Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M-shell of argon atoms, where experiments have been carried out using the so-called reconstruction of attosecond beating by the two-photon interference transitions technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon.
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21.
  • Dahlström, J. Marcus, 1982-, et al. (författare)
  • Theory of attosecond delays in laser-assisted photoionization
  • 2013
  • Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104 .- 1873-4421. ; 414, s. 53-64
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and an universal delay that originates from the probing process itself.
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22.
  • Dahlström, Marcus, et al. (författare)
  • Atomic and macroscopic measurements of attosecond pulse trains
  • 2009
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 80:3
  • Tidskriftsartikel (refereegranskat)abstract
    • We characterize attosecond pulses in a train using both the well established "reconstruction of attosecond beating by interference of two-photon transitions" (RABITT) technique and the recently demonstrated in situ method, which is based on a weak perturbation of the harmonic generation process by the second harmonic of the laser field. The latter technique determines the characteristics of the single atom emission, while RABITT allows one to measure attosecond pulses "on target." By comparing the results of the two methods, the influence of propagation and filtering on the attosecond pulses can be extracted.
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23.
  • Dahlström, Marcus (författare)
  • Light-Matter Interaction on the Attosecond Timescale
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Attosecond science refers to physical processes that occur on the natural timescale of electron motion in atomic and molecular systems. Attosecond time resolution can be obtained experimentally through a process called high-order harmonic generation where sharp attosecond pulses are formed in the time domain. Attosecond pulse trains contain many attosecond pulses with a constant pulse-to-pulse separation. The attosecond pulse trains provide a unique combination of temporal and spectral properties, since they correspond to coherent odd harmonics in the spectral domain. It is possible to use these temporal properties to ionize an atom at specific times, but it is also possible to use the spectral properties and tune a harmonic at a specific atomic resonance. In either case, the emitted photoelectrons can be probed with a coherent infrared field, and attosecond temporal information can be obtained. The work presented in this thesis shows that attosecond pulse trains can be used to study the phase variation of various two-photon ionization processes and, thus, the temporal properties of emitted photoelectrons. The delay in photoemission, the so-called Wigner delay, is discussed from a theoretical stand-point, and it is explained how it relates to the experimental method. The generation of attosecond pulses can be controlled using two-color laser fields for the high-order harmonic process. Experimental and theoretical results are presented, where the two-color field consists of a fundamental laser field, with an intensity of ~10^14 W/cm^2, and a second harmonic field with a relative intensity of ~10%. The delay between the two fields can be used to smoothly alter the spectral content, the divergence and the temporal properties of the attosecond pulses. Alternatively, when the second harmonic field is weak, ~0.1% relative intensity, it can be used to probe the one-color high-order harmonic generation process by considering the phase offset of the weak even-order harmonics. The established RABITT method is compared experimentally to the two-color probing technique and inconsistencies are reported close to the cutoff. Theoretical work presented in this thesis, shows that the inconsistencies can be explained using a quantum mechanical model for the two-color high-order harmonic generation. Finally, the transition from many attosecond pulses to few attosecond pulses using a second harmonic field in combination with a few-cycle fundamental laser field is reported.
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24.
  • Dahlström, Marcus, et al. (författare)
  • Quantum mechanical approach to probing the birth of attosecond pulses using a two-colour field
  • 2011
  • Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 44:9
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the generation of even and odd harmonics using an intense laser and a weak second harmonic field. Our theoretical approach is based on solving the saddle-point equations within the strong field approximation. The phase of the even harmonic oscillation as a function of the delay between the fundamental and second harmonic field is calculated and its variation with energy is found to be in good agreement with recent experimental results. We also find that the relationship between this phase variation and the group delay of the attosecond pulses depends on the intensity and wavelength of the fundamental field as well as the ionization potential of the atom.
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25.
  • Guenot, Diego, et al. (författare)
  • Measurements of relative photoemission time delays in noble gas atoms
  • 2014
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 47:24, s. 245602-
  • Tidskriftsartikel (refereegranskat)abstract
    • We determine relative photoemission time delays between valence electrons in different noble gas atoms (Ar, Ne and He) in an energy range between 31 and 37 eV. The atoms are ionized by an attosecond pulse train synchronized with an infrared laser field and the delays are measured using an interferometric technique. We compare our results with calculations using the random phase approximation with exchange and multi-configurational Hartree-Fock. We also investigate the influence of the different ionization angular channels.
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26.
  • Guenot, Diego, et al. (författare)
  • Photoemission time delay measurements and calculations close to the 3s ionization cross section minimum in ar
  • 2012
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:5, s. 053424-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present experimental measurements and theoretical calculations of photoionization time delays from the 3s and 3p shells in Ar in the photon energy range of 32-42 eV. The experimental measurements are performed by interferometry using attosecond pulse trains and the infrared laser used for their generation. The theoretical approach includes intershell correlation effects between the 3s and 3p shells within the framework of the random-phase approximation with exchange. The connection between single-photon ionization and the two-color two-photon ionization process used in the measurement is established using the recently developed asymptotic approximation for the complex transition amplitudes of laser-assisted photoionization. We compare and discuss the theoretical and experimental results, especially in the region where strong intershell correlations in the 3s -> kp channel lead to an induced Cooper minimum in the 3s ionization cross section.
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27.
  • He, Xinkui, et al. (författare)
  • Interference effects in two-color high-order harmonic generation
  • 2010
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 82:3
  • Tidskriftsartikel (refereegranskat)abstract
    • We study high-order harmonic generation in argon driven by an intense 800 nm laser field and a small fraction of its second harmonic. The intensity and divergence of the emitted even and odd harmonics are strongly modulated as a function of the relative delay between the two fields. We provide a detailed analysis of the underlying interference effects. The interference changes drastically when approaching the cutoff region due to a switch of the dominant trajectory responsible for harmonic generation.
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28.
  • Heuser, Sebastian, et al. (författare)
  • Angular dependence of photoemission time delay in helium
  • 2016
  • Ingår i: Physical Review A. - 2469-9926. ; 94:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Time delays of electrons emitted from an isotropic initial state with the absorption of a single photon and leaving behind an isotropic ion are angle independent. Using an interferometric method involving XUV attosecond pulse trains and an IR-probe field in combination with a detection scheme, which allows for full three-dimensional momentum resolution, we show that measured time delays between electrons liberated from the 1s(2) spherically symmetric ground state of helium depend on the emission direction of the electrons relative to the common linear polarization axis of the ionizing XUV light and the IR-probing field. Such time delay anisotropy, for which we measure values as large as 60 as, is caused by the interplay between final quantum states with different symmetry and arises naturally whenever the photoionization process involves the exchange of more than one photon. With the support of accurate theoretical models, the angular dependence of the time delay is attributed to small phase differences that are induced in the laser-driven continuum transitions to the final states. Since most measurement techniques tracing attosecond electron dynamics involve the exchange of at least two photons, this is a general and significant effect that must be taken into account in all measurements of time delays involving photoionization processes.
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29.
  • Horvath, Sebastian P., et al. (författare)
  • Noise-free on-demand atomic frequency comb quantum memory
  • 2021
  • Ingår i: Physical Review Research. - 2643-1564. ; 3:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an extension of the atomic frequency comb protocol that utilizes the Stark effect to perform noise-free, on-demand, control. An experimental realization of this protocol was implemented in the Pr3+:Y2SiO5 solid-state system, and a recall efficiency of 38% for a 0.8 μs storage time was achieved. Experiments were performed with both bright pulses as well as weak-coherent states, the latter achieving a signal-to-noise ratio of 570±120 using input pulses with an average photon number of ∼0.1. The principal limitation for a longer storage time was found to be the minimum peak width attainable for Pr3+:Y2SiO5. We employ an adaptation of an established atomic frequency comb model to investigate an on-demand, wide-bandwidth, memory based on Eu3+:Y2SiO5. From this, we determine that a storage time as long as 100 μs may be practical even without recourse to spin-wave storage.
  •  
30.
  • Isinger, M., et al. (författare)
  • Photoionization in the time and frequency domain
  • 2017
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 358:6365, s. 893-6
  • 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.
  •  
31.
  • Jiang, Wenyu, et al. (författare)
  • Resolving Quantum Interference Black Box through Attosecond Photoionization Spectroscopy
  • 2023
  • Ingår i: Physical Review Letters. - 0031-9007. ; 131:20
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiphoton light-matter interactions invoke a so-called "black box"in which the experimental observations contain the quantum interference between multiple pathways. Here, we employ polarization-controlled attosecond photoelectron metrology with a partial wave manipulator to deduce the pathway interference within this quantum 'black box"for the two-photon ionization of neon atoms. The angle-dependent and attosecond time-resolved photoelectron spectra are measured across a broad energy range. Two-photon phase shifts for each partial wave are reconstructed through the comprehensive analysis of these photoelectron spectra. We resolve the quantum interference between the degenerate p→d→p and p→s→p two-photon ionization pathways, in agreement with our theoretical simulations. Our approach thus provides an attosecond time-resolved microscope to look inside the "black box"of pathway interference in ultrafast dynamics of atoms, molecules, and condensed matter.
  •  
32.
  • Klünder, Kathrin, et al. (författare)
  • Probing Single-Photon Ionization on the Attosecond Time Scale
  • 2011
  • Ingår i: Physical Review Letters. - 1079-7114. ; 106:14
  • Tidskriftsartikel (refereegranskat)abstract
    • We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s(2) and from the 3p(6) shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.
  •  
33.
  •  
34.
  • Kotur, Marija, et al. (författare)
  • Spectral phase measurement of a Fano resonance using tunable attosecond pulses
  • 2016
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.
  •  
35.
  • Larsson, Stefan, et al. (författare)
  • A complementary field study on the uniformity of lime-cement columns for deep mixing
  • 2005
  • Ingår i: Ground Improvement. - : Thomas Telford. - 1365-781X .- 1751-7621. ; 9:2, s. 67-77
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents results from work concerning development of the installation technique of lime-cement columns for ground improvement by deep mixing, as a part of the work of the Swedish Deep Stabilization Research Centre. A second field test was performed in order to test the findings from a previous work published by Larsson et al. The same methodology was adopted as in the previous work. However, the experimental programme was somewhat modified. Statistical analysis of variances, ANOVA, was used to investigate the influence of a number of factors in the mixing process: retrieval rate; number of mixing blades; rotation speed; air pressure in the binder tank; and diameter of the binder outlet hole. The analysis was performed with respect to the stabilisation effect and the coefficient of variation evaluated from hand-operated penetrometer tests on excavated column sections in open test pits. The retrieval rate and the number of mixing blades were found to have a significant effect. The effect of rotation speed, the binder tank air pressure, and the diameter of the outlet hole were insignificant. The two field studies illustrate the importance of performing a sufficient number of tests when studying influencing factors, because the strength is highly stochastic with large variations.
  •  
36.
  • Larsson, Stefan, et al. (författare)
  • Uniformity of lime-cement columns for deep mixing : A field study
  • 2005
  • Ingår i: Ground Improvement. - : Thomas Telford. - 1365-781X .- 1751-7621. ; 9:1, s. 1-15
  • Tidskriftsartikel (refereegranskat)abstract
    • A field study of the mixing process of lime-cement columns for deep mixing has been carried out at a test site in Håby, Sweden. The study aimed to investigate the influence on the stabilisation effect and the coefficient of variation for excavated columns, when a number of factors related to the installation process were varied. The influencing factors investigated were the retrieval rate, number of mixing blades, rotational speed, air pressure in the storage tank, and diameter of the binder outlet hole. A large number of hand-operated penetrometer tests were carried out on the excavated column cross-sections. Statistical multifactor analyses were used to evaluate the influence on the stabilisation effect and the coefficient of variation of the varied factors. The results showed that the retrieval rate and the number of mixing blades were found to have a significant effect. The effect of rotational speed and the diameter of the outlet hole were found to be insignificant. The field study showed that the strength and deformation properties of the soil and the upper pair of mixing blades, with respect to the binder outlet hole, had a major influence on the binder dispersion over the column cross-section. The blade rotation number can be used as an indirect value of the mixing work and can be used as a measure of the mixing tool effectiveness.
  •  
37.
  • Liao, Yijie, et al. (författare)
  • Circularly polarized RABBITT applied to a Rabi-cycling atom
  • 2024
  • Ingår i: Physical Review A. - 2469-9926. ; 109:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We utilize the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) technique to study the phase of a Rabi-cycling atom using circularly polarized extreme ultraviolet and infrared fields, where the infrared field induces Rabi oscillations between the 2s and 2p states of lithium. Autler-Townes splittings are observed in sidebands of the photoelectron spectra and the relative phases of outgoing electron wave packets are retrieved from the azimuthal angle. In this RABBITT scheme, more ionization pathways beyond the usual two-photon pathways are required. Our results show that the polar-angle-integrated and polar-angle-resolved RABBITT phases have different behaviors when the extreme ultraviolet and infrared fields have co- and counter-rotating circular polarizations, which are traced back to the different ionization channels according to the selection rules in these two cases and their competition relying on the propensity rule in laser-assisted photoionization.
  •  
38.
  • Linde, Cecilia, et al. (författare)
  • Gender, underutilization of cardiac resynchronization therapy, and prognostic impact of QRS prolongation and left bundle branch block in heart failure.
  • 2015
  • Ingår i: Europace. - : Oxford University Press. - 1099-5129 .- 1532-2092. ; 17:3, s. 424-431
  • Tidskriftsartikel (refereegranskat)abstract
    • AIMS: It has been suggested that cardiac resynchronization therapy (CRT) is less utilized, dyssynchrony occurs at narrower QRS, and CRT is more beneficial in women compared with men. We tested the hypotheses that (i) CRT is more underutilized and (ii) QRS prolongation and left bundle branch block (LBBB) are more harmful in women.METHODS AND RESULTS: We studied 14 713 patients (28% women) with left ventricular ejection fraction (LVEF) <40% in the Swedish Heart Failure Registry. In women vs. men, CRT was present in 4 vs. 7% (P < 0.001) and was absent but with indication in 30 vs. 31% (P = 0.826). Next, among 13 782 patients (28% women) without CRT, 9% of women and 17% of men had non-specific intraventricular conduction delay (IVCD) and 27% of women and 24% of men had LBBB. One-year survival with narrow QRS was 85% in women and 88% in men, with IVCD 74 and 78%, and with LBBB 84 and 82%, respectively. Compared with narrow QRS, IVCD had a multivariable hazard ratio of 1.24 (95% CI 1.05-1.46, P = 0.011) in women and 1.30 (95% CI 1.19-1.42, P < 0.001) in men, and LBBB 1.03 (95% CI 0.91-1.16, P = 0.651) in women and 1.16 (95% CI 1.07-1.26, P < 0.001) in men, P for interaction between gender and QRS morphology, 0.241.CONCLUSIONS: While the proportion with CRT was lower in women, CRT was equally underutilized in both genders. QRS prolongation with or without LBBB was not more harmful in women than in men. Efforts to improve CRT implementation should be directed equally towards women and men.
  •  
39.
  • Lindroth, Eva, et al. (författare)
  • Attosecond delays in laser-assisted photodetachment from closed-shell negative ions
  • 2017
  • Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 96:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We study laser-assisted photodetachment time delays by attosecond pulse trains from the closed-shell negative ions F- and Cl. We investigate the separability of the delay into two contributions: (i) the Wigner-like delay associated with one-photon ionization by the attosecond pulse train and (ii) the delay associated with the exchange of an additional laser photon in the presence of the potential of the remaining target. Based on the asymptotic form of the wave packet, the latter term is expected to be negligible because the ion is neutralized, leading to a vanishing laser-ion interaction with increasing electron-atom separation. While this asymptotic behavior is verified at high photoelectron energies, we also quantify sharp deviations at low photoelectron energies. Further, these low-energy delays are clearly different for the two studied anions, indicating a breakdown of the universality of laser-ion-induced delays. The fact that the short-range potential can induce a delay of as much as 50 as can have implications for the interpretation of delay measurements also in other systems that lack long-range potential.
  •  
40.
  • Lund, Lars H., et al. (författare)
  • Age, prognostic impact of QRS prolongation and left bundle branch block, and utilization of cardiac resynchronization therapy: findings from 14713 patients in the Swedish Heart Failure Registry
  • 2014
  • Ingår i: European Journal of Heart Failure. - : Oxford University Press (OUP): Policy B / Wiley. - 1388-9842 .- 1879-0844. ; 16:10, s. 1073-1081
  • Tidskriftsartikel (refereegranskat)abstract
    • AimsAge is not a contraindication to cardiac resynchronization therapy (CRT), but the prevalence and prognostic impact of QRS prolongation with intraventricular conduction delay (IVCD) and left bundle branch block (LBBB), as well as CRT utilization, may differ with age. We tested the hypotheses that in the elderly: (i) IVCD and LBBB are more prevalent, (ii) IVCD and LBBB are more harmful, and (iii) CRT is underutilized. Methods and resultsWe studied 14713 patients with ejection fraction 39% in the Swedish Heart Failure Registry and divided into age groups 65years, 66-80years and greater than80years. Among 13782 patients without CRT, IVCD was present in the three age groups in 11% vs. 15% vs. 19% and LBBB was present in 20% vs. 27% vs. 28%, respectively, (Pless than0.001). The multivariable hazard ratio (HR) for all-cause mortality over a median (interquartile range) follow-up of 29 (12-53) months for IVCD vs. narrow QRS was 1.31 (1.06-1.63, P=0.013) in the 65year group, 1.32 (1.17-1.47, Pless than0.001) in the 66-80year group, and 1.26 (1.21-1.41, pless than0.001) in the greater than80year group. For LBBB vs. narrow QRS it was 1.29 (1.07-1.56, P=0.009), 1.17 (1.06-1.30, P=0.002), and 1.10 (0.99-1.22, P=0.091), respectively. The adjusted P for interaction between age and QRS morphology was 0.664. In the three age groups, CRT was present in 6% vs. 8% vs. 4% and absent but with indication in 23% vs. 32% vs. 37%, respectively (Pless than0.001). ConclusionsBoth IVCD and LBBB were more common with increasing age and were similarly strong independent predictors of mortality and in all ages. The underutilization of CRT was worse with increasing age.
  •  
41.
  • Lund, Lars H, et al. (författare)
  • Association between demographic, organizational, clinical, and socio-economic characteristics and underutilization of cardiac resynchronization therapy : results from the Swedish Heart Failure Registry.
  • 2017
  • Ingår i: European Journal of Heart Failure. - : John Wiley & Sons. - 1388-9842 .- 1879-0844. ; 19:10, s. 1270-1279
  • Tidskriftsartikel (refereegranskat)abstract
    • AIMS: Cardiac resynchronization therapy (CRT) improves outcomes in heart failure (HF) but may be underutilized. The reasons are unknown.METHODS AND RESULTS: We linked the Swedish Heart Failure Registry to national registries with ICD-10 (International Classification of Diseases-10th Revision) co-morbidity diagnoses and demographic and socio-economic data. In patients with EF ≤39% and NYHA II-IV, we assessed prevalence of CRT indication and CRT use. In those with CRT indication, we assessed the association between 37 potential baseline covariates and CRT non-use using multivariable generalized estimating equation (GEE) models. Of 12 807 patients (mean age 71 ± 12 years, 28% female), 841 (7%) had CRT, 3094 (24%) had an indication for but non-use of CRT, and 8872 (69%) had no indication. Important variables independently associated with CRT non-use were: HF duration <6 months [risk ratio (RR) 1.21, 95% confidence interval (CI) 1.17-1.24]; non-cardiology planned follow-up (RR 1.14, 95% CI 1.09-1.18); age >75 years (RR 1.13, 95% CI 1.09-1.18); non-cardiology care at baseline (RR 1.10, 95% CI 1.07-1.14); small-town non-university centre (RR 1.08, 95% CI 1.05-1.12); female sex (RR 1.07 95% CI 1.03-1.10) (all P < 0.05); as was absence of AF, living alone; psychiatric diagnosis; smoking; and non-use of HF drugs. Education, income, cancer, or HF characteristics were not independently associated with CRT non-use.CONCLUSION: In this population-wide HF registry, CRT was underutilized. Non-use was associated mostly with demographic and organizational, but not clinical or socio-economic factors. This calls for programmes to raise awareness of CRT indications and improve access and referrals to cardiology specialists.
  •  
42.
  • Lund, Lars H., et al. (författare)
  • Effect of expanding evidence and evolving clinical guidelines on the prevalence of indication for cardiac resynchronization therapy in patients with heart failure
  • 2018
  • Ingår i: European Journal of Heart Failure. - : WILEY. - 1388-9842 .- 1879-0844. ; 20:4, s. 769-777
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: To assess the prevalence of indication for cardiac resynchronization therapy (CRT) in patients with heart failure (HF) and reduced ejection fraction (EF) when recommendations from evolving European Society of Cardiology (ESC) guidelines are considered.Methods and results: Unique patients (n=17 193) with EF <= 39% and key data available for evaluation of CRT indication from the Swedish HF Registry were included. Indication for CRT was defined as either CRT implanted or CRT device absent but fulfilling criteria for class I-IIa recommendations in ESC guidelines published between 2005/2007 and 2016. Prevalence was calculated as the ratio of patients with CRT indication to the study population. The prevalence of CRT indication increased from 24.5% when the 2005/2007 ESC guidelines were considered to a peak of 30.0% when the 2013 ESC guidelines were considered (P<0.001, 22.4% relative increase). Compared to the 2013 ESC guidelines, the prevalence declined significantly when the 2016 ESC guidelines were used as determinant for CRT indication (26.8%, 10.7% relative reduction, P<0.001). Actual CRT utilization was 6.8%.Conclusion: Among patients with HF and reduced EF, the prevalence of CRT indication increased significantly comparing recommendations from ESC guidelines published between 2005/2007 and 2013, but then declined when the 2016 ESC guidelines were considered. The 2005-2013 increase may reflect the expansion of documented CRT efficacy to New York Heart Association class II, whereas the subsequent drop likely results from the more stringent criteria for QRS duration in the 2016 ESC guidelines. Actual CRT utilization is lower than indicated, regardless of which guidelines are considered.
  •  
43.
  • Mansten, Erik, et al. (författare)
  • Spectral shaping of attosecond pulses using two-colour laser fields
  • 2008
  • Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • We use a strong two-colour laser field composed of the fundamental (800 nm) and the second harmonic (400 nm) of an infrared (IR) laser field to generate attosecond pulses with controlled spectral and temporal properties. With a second-harmonic intensity equal to 15% of the IR intensity the second-harmonic field is strong enough to significantly alter and control the electron trajectories in the generation process. This enables us to tune the central photon energy of the attosecond pulses by changing the phase difference between the IR and the second-harmonic fields. In the time domain the radiation is emitted as a sequence of pulses separated by a full IR cycle. We also perform calculations showing that the effect of even stronger second-harmonic fields leads to an extended tunable range under conditions that are experimentally feasible.
  •  
44.
  • Mansten, Erik, et al. (författare)
  • Spectral signature of short attosecond pulse trains.
  • 2009
  • Ingår i: Physical Review Letters. - 1079-7114. ; 102:8
  • Tidskriftsartikel (refereegranskat)abstract
    • We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800 nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.
  •  
45.
  • Mauritsson, Johan, et al. (författare)
  • Attosecond electron interferometry
  • 2013
  • Ingår i: Attosecond Physics : Attosecond Measurements and Control of Physical Systems - Attosecond Measurements and Control of Physical Systems. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1556-1534 .- 0342-4111. - 9783642376221 - 9783642376238 ; 177, s. 121-134
  • Bokkapitel (refereegranskat)abstract
    • Attosecond extreme ultraviolet light pulses have the potential to resolve the ultrafast electron dynamics that govern basic properties of atoms, molecules, and solids. Here we present three different interferometric pump-probe methods aiming to access not only the temporal dynamics, but also state specific phase information after excitation/ionization using attosecond pulses.
  •  
46.
  • Mauritsson, Johan, et al. (författare)
  • Laserteknik berättar elektronernas dramatik
  • 2010
  • Ingår i: Fysikaktuellt. - 0283-9148. ; :4, s. 10-10
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • Attofysik handlar om att öppna ögonen för en värld som vi länge vetat fanns men fram till nu inte har kunnat se – elektronernas värld. En värld av ofattbart små och snabba förlopp och fenomen. Utvecklingen av lasertekniken har kommit så långt att vi faktiskt har möjlighet att studera den världen.
  •  
47.
  • Mauritsson, Johan, et al. (författare)
  • Sub-cycle control of attosecond pulse generation using two-colour laser fields
  • 2009
  • Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:13
  • Konferensbidrag (refereegranskat)abstract
    • Strong field laser-matter interaction is intrinsically a sub-cycle phenomenon, which is clearly illustrated by the generation of attosecond pulses through the high-order harmonic process. Therefore, to control strong field processes the structure of the field driving the generation has to be controlled on a sub-cycle level. One approach is to use phase stabilized few-cycle driving pulses and vary the carrier-envelope phase of these pulses; an alternative method is to use longer pulses and include the second harmonic to tailor the field structure.
  •  
48.
  • Månsson, Erik, et al. (författare)
  • Double ionization probed on the attosecond timescale
  • 2014
  • Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 10:3, s. 207-211
  • Tidskriftsartikel (refereegranskat)abstract
    • Double ionization following the absorption of a single photon is one of the most fundamental processes requiring interaction between electrons(1-3). Information about this interaction is usually obtained by detecting emitted particles without access to real-time dynamics. Here, attosecond light pulses(4,5), electron wave packet interferometry(6) and coincidence techniques(7) are combined to measure electron emission times in double ionization of xenon using single ionization as a clock, providing unique insight into the two-electron ejection mechanism. Access to many-particle dynamics in real time is of fundamental importance for understanding processes induced by electron correlation in atomic, molecular and more complex systems.
  •  
49.
  • Nandi, Saikat, et al. (författare)
  • Generation of entanglement using a short-wavelength seeded free-electron laser
  • 2024
  • Ingår i: Science Advances. - 2375-2548. ; 10:16, s. 0668-0668
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantum entanglement between the degrees of freedom encountered in the classical world is challenging to observe due to the surrounding environment. To elucidate this issue, we investigate the entanglement generated over ultrafast timescales in a bipartite quantum system comprising two massive particles: a free-moving photoelectron, which expands to a mesoscopic length scale, and a light-dressed atomic ion, which represents a hybrid state of light and matter. Although the photoelectron spectra are measured classically, the entanglement allows us to reveal information about the dressed-state dynamics of the ion and the femtosecond extreme ultraviolet pulses delivered by a seeded free-electron laser. The observed generation of entanglement is interpreted using the time-dependent von Neumann entropy. Our results unveil the potential for using short-wavelength coherent light pulses from free-electron lasers to generate entangled photoelectron and ion systems for studying spooky action at a distance.
  •  
50.
  • Nandi, Saikat, et al. (författare)
  • Generation of entanglement using a short-wavelength seeded free-electron laser
  • 2024
  • Ingår i: SCIENCE ADVANCES. - 2375-2548. ; 10:16
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantum entanglement between the degrees of freedom encountered in the classical world is challenging to observe due to the surrounding environment. To elucidate this issue, we investigate the entanglement generated over ultrafast timescales in a bipartite quantum system comprising two massive particles: a free-moving photoelectron, which expands to a mesoscopic length scale, and a light-dressed atomic ion, which represents a hybrid state of light and matter. Although the photoelectron spectra are measured classically, the entanglement allows us to reveal information about the dressed-state dynamics of the ion and the femtosecond extreme ultraviolet pulses delivered by a seeded free-electron laser. The observed generation of entanglement is interpreted using the time-dependent von Neumann entropy. Our results unveil the potential for using short-wavelength coherent light pulses from free-electron lasers to generate entangled photoelectron and ion systems for studying spooky action at a distance.
  •  
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