| 1. |
- L'Huillier, A., et al.
(author)
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Atomic physics with attosecond pulses
- 2006
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In: International Conference on Ultrafast Phenomena, UP 2006. - 1557528101 - 9781557528100
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Conference paper (peer-reviewed)
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| 2. |
- Maroju, P. K., et al.
(author)
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Analysis of two-color photoelectron spectroscopy for attosecond metrology at seeded free-electron lasers
- 2021
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 23:4
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Journal article (peer-reviewed)abstract
- The generation of attosecond pulse trains at free-electron lasers opens new opportunities in ultrafast science, as it gives access, for the first time, to reproducible, programmable, extreme ultraviolet (XUV) waveforms with high intensity. In this work, we present a detailed analysis of the theoretical model underlying the temporal characterization of the attosecond pulse trains recently generated at the free-electron laser FERMI. In particular, the validity of the approximations used for the correlated analysis of the photoelectron spectra generated in the two-color photoionization experiments are thoroughly discussed. The ranges of validity of the assumptions, in connection with the main experimental parameters, are derived.
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| 3. |
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| 4. |
- Makos, I., et al.
(author)
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Attosecond photoelectron spectroscopy using high-harmonic generation and seeded free-electron lasers
- 2023
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In: 2023 Photonics North, PN 2023. - 9798350326734
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Conference paper (peer-reviewed)abstract
- In this work, we use attosecond time-resolved techniques to investigate photoionization dynamics on its natural timescale, employing both high harmonic generation and seeded free-electron lasers to generate extreme ultraviolet attosecond pulse trains for our studies. With the former approach, we examine the role of nuclear motion in molecular photoionization dynamics, while with the latter we introduce a novel attosecond timing tool for single-shot characterization of the relative phase between the XUV and the infrared field.
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| 5. |
- Sansone, G., et al.
(author)
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Attosecond excitation of electron wavepackets
- 2008
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In: Quantum Electronics and Laser Science Conference, QELS 2008. - 9781557528599
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Conference paper (peer-reviewed)abstract
- We present experiments, supported by time-dependent Schrödinger simulations, on the dynamics of Helium bound states after an attosecond excitation in the presence of a strong infrared laser field.
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| 6. |
- Varju, Katalin, et al.
(author)
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Angularly resolved electron wave packet interferences
- 2006
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:18, s. 3983-3991
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Journal article (peer-reviewed)abstract
- We study experimentally the ionization of argon atoms by a train of attosecond pulses in the presence of a strong infrared laser field, using a velocity map imaging technique. The recorded momentum distribution strongly depends on the delay between the attosecond pulses and the laser field. We interpret the interference patterns observed for different delays using numerical and analytical calculations within the strong field approximation.
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| 7. |
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| 8. |
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| 9. |
- Klünder, Kathrin, et al.
(author)
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Reconstruction of attosecond electron wave packets using quantum state holography
- 2013
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In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 88:3
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Journal article (peer-reviewed)abstract
- We present a method for performing quantum state holography, with which we completely characterize the amplitude and phase of an attosecond electron wave packet. Our approach is an extension of a recent publication [J. Mauritsson et al., Phys. Rev. Lett. 105, 053001 (2010)] in which we demonstrated experimentally that the energies and amplitudes of an attosecond electron wave packet can be characterized using attosecond electron interferometry. Here we show theoretically that attosecond electron interferometry can be extended to retrieve the phases of all the states that make up the wave packet. We demonstrate the feasibility of our method by analyzing a wave packet created by a shake-up process. We show that our method can successfully retrieve arbitrary phases and/or lifetimes added to the component eigenstates.
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| 10. |
- Maroju, Praveen Kumar, et al.
(author)
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Attosecond coherent control of electronic wave packets in two-colour photoionization using a novel timing tool for seeded free-electron laser
- 2023
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 17, s. 200-207
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Journal article (peer-reviewed)abstract
- In ultrafast spectroscopy, the temporal resolution of time-resolved experiments depends on the duration of the pump and probe pulses, and on the control and characterization of their relative synchronization. Free-electron lasers operating in the extreme ultraviolet and X-ray spectral regions deliver pulses with femtosecond and attosecond duration in a broad array of pump-probe configurations to study a wide range of physical processes. However, this flexibility, together with the large dimensions and high complexity of the experimental set-ups, limits control of the temporal delay to the femtosecond domain, thus precluding a time resolution below the optical cycle. Here we demonstrate a novel single-shot technique able to determine the relative synchronization between an attosecond pulse train-generated by a seeded free-electron laser-and the optical oscillations of a near-infrared field, with a resolution of one atomic unit (24 as). Using this attosecond timing tool, we report the first example of attosecond coherent control of photoionization in a two-colour field by manipulating the phase of high-order near-infrared transitions.
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| 11. |
- Mauritsson, Johan, et al.
(author)
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Attosecond Electron Spectroscopy Using a Novel Interferometric Pump-Probe Technique
- 2010
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In: Physical Review Letters. - 1079-7114. ; 105:5
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Journal article (peer-reviewed)abstract
- We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse (AP) with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original AP. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multipath interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the AP duration.
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| 12. |
- S. Zamith, V. Blanchet, B. Girard, J. Norin, J. Mauritsson, A. l'Huillier, J. Andersson, S. L. Sorensen, I. Hjelte, O. Björneholm and D. Gauyacq
(author)
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The predissociation of highly excited states in acetylene by time-resolved photoelectron spectroscopy
- 2003
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In: Journal of Chemical Physics. ; :119, s. 3763-
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Journal article (peer-reviewed)
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| 13. |
- Bengtsson, S., et al.
(author)
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Space–time control of free induction decay in the extreme ultraviolet
- 2017
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In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 11:4, s. 252-258
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Journal article (peer-reviewed)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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| 14. |
- Carré, B., et al.
(author)
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Characterization of attosecond pulse trains
- 2007
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In: Ultrafast Optics V. - New York, NY : Springer New York. - 1556-1534 .- 0342-4111. - 9780387491172 ; 132, s. 45-56
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Conference paper (peer-reviewed)abstract
- Ultrashort light pulses, as short as 100 as, can be produced from high harmonic generation (HHG) in an atomic gas medium. This major achievement of the last 6 years in high field physics has now been demonstrated in different conditions of medium-field interaction [1].
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| 15. |
- Gisselbrecht, M., et al.
(author)
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Attosecond insight into electron correlation
- 2019
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In: Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conference, CLEO/Europe-EQEC 2015. - 9781467374750
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Conference paper (peer-reviewed)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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| 16. |
- Guenot, Diego, et al.
(author)
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Probing electron correlation on the attosecond time scale
- 2014
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In: High Intensity Lasers and High Field Phenomena, HILAS 2014. - 9781557529954
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Conference paper (peer-reviewed)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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| 17. |
- Harth, A., et al.
(author)
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Few-cycle high-repetition rate OPCPA for multiphoton PEEM towards atto-PEEM
- 2016
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In: International Conference on Ultrafast Phenomena, UP 2016. - 9781943580187 ; Part F20-UP 2016
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Conference paper (peer-reviewed)abstract
- We present a few-cycle high-repetition rate optical parametric amplifier for multiphoton PEEM experiments on semiconductor nanowires. This parametric amplifier is also used for the generation of high-order harmonics at 200kHz for future atto-PEEM experiments.
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| 18. |
- Johnsson, Per, et al.
(author)
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Attosecond electron wave packet dynamics in strong laser fields
- 2005
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In: Physical Review Letters. - 1079-7114. ; 95:1, s. 1-013001
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Journal article (peer-reviewed)abstract
- We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (similar to 20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes.
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| 19. |
- Kumar Maroju, Praveen, et al.
(author)
-
Attosecond pulse shaping using a seeded free-electron laser
- 2020
-
In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 578, s. 386-391
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Journal article (peer-reviewed)abstract
- Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales. The reproducible generation and characterization of attosecond waveforms has been demonstrated so far only through the process of high-order harmonic generation. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters, multilayer mirrors and manipulation of the driving field. However, none of these approaches allows the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free-electron lasers, by contrast, deliver femtosecond, extreme-ultraviolet and X-ray pulses with energies ranging from tens of microjoules to a few millijoules. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers.
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| 20. |
- Lopez, Rodrigo, et al.
(author)
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Amplitude and phase control of attosecond light pulses
- 2005
-
In: Physical Review Letters. - 1079-7114. ; 94:3
-
Journal article (peer-reviewed)abstract
- We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms.
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| 21. |
- Maroju, Praveen K., et al.
(author)
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A Novel Attosecond Timing Tool for Free-Electron Laser Experiment
- 2020
-
In: High Intensity Lasers and High Field Phenomena 2020. - 9781943580736
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Conference paper (peer-reviewed)abstract
- We demonstrate a novel timing tool for Free-Electron Lasers to determine the delay between an attosecond pulse train and infrared pulse with sub-optical-cycle resolu-. tion.
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| 22. |
- Maroju, Praveen Kumar, et al.
(author)
-
Complex attosecond waveform synthesis at fel fermi
- 2021
-
In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 11:21
-
Journal article (peer-reviewed)abstract
- Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields.
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| 23. |
- Olofsson, A., et al.
(author)
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Opto-optical modulator (OOM) for extreme ultraviolet pulses
- 2020. - 7
-
In: Attosecond Physics. - : IOP Publishing. - 1742-6588. ; 1412
-
Conference paper (peer-reviewed)abstract
- There is a profound, almost symbiotic relation between electrons and photons. When light interacts with matter the electrons in the material will start to move and oscillate. When a charged particle, such as an electron, oscillates it will act as a dipole and emit light. We utilize this symbiotic relation and extend the control of light to the extreme ultraviolet (XUV) region using the newly developed XUV opto-optical modulator.
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| 24. |
- Petersson, C. L M, et al.
(author)
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Phase metrology with multi-cycle two-colour pulses
- 2016
-
In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 49:9
-
Journal article (peer-reviewed)abstract
- Strong-field phenomena driven by an intense infrared (IR) laser depend on during what part of the field cycle they are initiated. By changing the sub-cycle character of the laser electric field it is possible to control such phenomena. For long pulses, sub-cycle shaping of the field can be done by adding a relatively weak, second harmonic of the driving field to the pulse. Through constructive and destructive interference, the combination of strong and weak fields can be used to change the probability of a strong-field process being initiated at any given part of the cycle. In order to control sub-cycle phenomena with optimal accuracy, it is necessary to know the phase difference of the strong and the weak fields precisely. If the weaker field is an even harmonic of the driving field, electrons ionized by the field will be asymmetrically distributed between the positive and negative directions of the combined fields. Information about the asymmetry can yield information about the phase difference. A technique to measure asymmetry for few-cycle pulses, called stereo-ATI (above threshold ionization), has been developed by Paulus et al (2003 Phys. Rev. Lett. 91 253004). This paper outlines an extension of this method to measure the phase difference between a strong IR and its second harmonic.
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| 25. |
- Remetter, Thomas, et al.
(author)
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Attosecond electron wave packet interferometry
- 2006
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In: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 2:5, s. 323-326
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Journal article (peer-reviewed)abstract
- A complete quantum-mechanical description of matter and its interaction with the environment requires detailed knowledge of a number of complex parameters. In particular, information about the phase of wavefunctions is important for predicting the behaviour of atoms, molecules or larger systems. In optics, information about the evolution of the phase of light in time(1) and space(2) is obtained by interferometry. To obtain similar information for atoms and molecules, it is vital to develop analogous techniques. Here we present an interferometric method for determining the phase variation of electronic wave packets in momentum space, and demonstrate its applicability to the fundamental process of single-photon ionization. We use a sequence of extreme-ultraviolet attosecond pulses(3,4) to ionize argon atoms and an infrared laser field, which induces a momentum shear(5) between consecutive electron wave packets. The interferograms that result from the interaction of these wave packets provide useful information about their phase. This technique opens a promising new avenue for reconstructing the wavefunctions(6,7) of atoms and molecules and for following the ultrafast dynamics of electronic wave packets.
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