| 1. |
- 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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| 2. |
- 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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| 3. |
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| 4. |
- 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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| 5. |
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| 6. |
- 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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| 7. |
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| 8. |
- Turconi, M., et al.
(författare)
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Spin-orbit-resolved spectral phase measurements around a Fano resonance
- 2020
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:18
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Tidskriftsartikel (refereegranskat)abstract
- We apply a spectrally-resolved electron interferometry technique to the measurement of the spectral phase in the vicinity of the 3s(1)3p(6)4p Fano resonance of argon. We show that it allows disentangling the phases of the two nearly-overlapping electron wavepackets corresponding to different spin-orbit final states. Using simple assumptions, it is possible to process the experimental data and numerically isolate each component in a self-consistent manner. This in turn allows reconstructing the autoionization dynamics of the dominant channel.
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| 9. |
- 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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| 10. |
- 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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