| 1. |
- Cui, Jun Jie, et al.
(författare)
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Proposal for Observing XUV-Induced Rabi Oscillation Using Superfluorescent Emission
- 2023
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 131:4
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Tidskriftsartikel (refereegranskat)abstract
- Intense x-ray and extreme ultraviolet (XUV) light sources have been available for decades, however, due to weak nonlinear interaction in the XUV photon energy range, observation of Rabi oscillation induced by XUV pulse remains a very challenging experimental task. Here we suggest a scheme where photoionization of a He medium by an intense XUV pump pulse is followed by a strong population inversion and Rabi oscillation at the He+(1s-3p) transition and is accompanied by superfluorescence (SF) of the 7.56 eV pulse at the He+(3p-2s) transition. Our numerical simulations show that the Rabi oscillation at the He+(1s-3p) transition induced by an XUV pulse with photon energy 48.36 eV results in significant signatures in the SF spectra, allowing us to identify and characterize the XUV induced Rabi-oscillatory regime. The proposed scheme provides a sensitive tool to monitor and control ultrafast nonlinear dynamics in atoms and molecules triggered by intense XUV.
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| 2. |
- Kimberg, Victor, et al.
(författare)
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Amplified X-Ray Emission from Core-Ionized Diatomic Molecules
- 2013
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 110:4
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Tidskriftsartikel (refereegranskat)abstract
- We predict high-gain x-ray lasing in molecular nitrogen by ultrafast core ionization with an x-ray free-electron laser source. To estimate the spectral and temporal output of this molecular x-ray laser, we solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. The spectrum of the amplified x-ray emission shows a strong dependence on the gain-length product. Whereas the emission at small gain length is similar to the relatively broad x-ray fluorescence band, the spectrum is determined by a single frequency in the linear gain region. The vibrational wave packet dynamics during the x-ray emission process is examined. By preparation of the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band. The present scheme is applicable to other homo- and heteronuclear diatomic systems, thereby extending the spectral range of coherent x-ray radiation sources based on amplification on bound transitions.
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| 3. |
- Kimberg, Victor, et al.
(författare)
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Stimulated X-ray Raman scattering : a critical assessment of the building block of nonlinear X-ray spectroscopy
- 2016
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Ingår i: Faraday discussions. - : Royal Society of Chemistry. - 1359-6640 .- 1364-5498.
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Tidskriftsartikel (refereegranskat)abstract
- With the invention of femtosecond X-ray free-electron lasers (XFELs), studies of light-induced chemical reaction dynamics and structural dynamics reach a new era, allowing for time-resolved X-ray diffraction and spectroscopy. To ultimately probe coherent electron and nuclear dynamics on their natural time and length scales, coherent nonlinear X-ray spectroscopy schemes have been proposed. In this contribution, we want to critically assess the experimental realisation of nonlinear X-ray spectroscopy at current-day XFEL sources, by presenting first experimental attempts to demonstrate stimulated resonant X-ray Raman scattering in molecular gas targets.
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| 4. |
- Kimberg, Victor, et al.
(författare)
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X-ray lasing in diatomic molecules
- 2014
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 488:1
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Tidskriftsartikel (refereegranskat)abstract
- We predict high-gain x-ray lasing in diatomic molecules by ultrafast core ionization of the C K- and O K-edges in CO and the N K-edge in N2 with an x-ray free-electron laser source. To estimate the spectral and temporal output of this molecular x-ray laser, we solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. Despite the broad fluorescence bandwidth, the amplified x-ray emission shows a narrow spectrum. By controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization and emission energy control of the x-ray laser radiation is achievable.
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| 5. |
- Kimberg, Victor, et al.
(författare)
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X-ray lasing in the CO molecule
- 2013
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Ingår i: Journal of Physics B. - : Institute of Physics (IOP). - 0953-4075 .- 1361-6455. ; 46:16
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically demonstrate the feasibility of x-ray lasing in the CO molecule by the core ionization of the C K- and O K-shell by x-ray free-electron laser sources. Our numerical simulations are based on the solution of generalized Maxwell–Bloch equations, accounting for the electronic and nuclear degrees of freedom. The amplified x-ray emission pulses have an extremely narrow linewidth of about 0.1 eV and a pulse duration shorter than 30 fs. We compare x-ray lasing transitions to the three lowest electronic states of singly ionized CO. The dependence of the lasing efficiency on the spectral width of the x-ray fluorescence band, value and orientation of the electronic transition dipole moment, lifetime of the core-excited state and the duration of the pump pulse is analysed. Using a pre-aligned molecular ensemble substantially increases the amplified emission. Moreover, by controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization, the control of the emitted x-ray radiation is achievable. Preparing the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band. The present scheme is applicable to other diatomic systems, thereby extending the spectral range of coherent x-ray radiation sources based on stimulated x-ray emission on bound transitions.
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| 6. |
- Rohringer, Nina, et al.
(författare)
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Atomic and Molecular Inner-Shell X-Ray Lasers
- 2012
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Ingår i: Frontiers in Optics 2012/Laser Science XXVIII. - : OSA. - 9781557529565
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Konferensbidrag (refereegranskat)abstract
- We present experimental results on the first realization of an atomic inner-shell x-ray laser and x-ray Raman laser in the KeV photon-energy regime in Neon. Extension of the scheme to diatomic molecules is discussed.
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| 7. |
- You, Jhih-An, et al.
(författare)
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Attosecond dynamics of light-induced resonant hole transfer in high-order-harmonic generation
- 2017
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Ingår i: Physical Review A. - 2469-9926. ; 95:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of high-order-harmonic generation (HHG) assisted by extreme ultraviolet (XUV) attosecond pulses, which can lead to the excitation of inner-shell electrons and the generation of a second HHG plateau. With the treatment of a one-dimensional model of krypton, based on time-dependent configuration interaction singles (TDCIS) of an effective two-electron system, we show that the XUV-assisted HHG spectrum reveals the duration of the semiclassical electron trajectories. The results are interpreted by the strong-field approximation (SFA) and the importance of the hole transfer during the tunneling process is emphasized. Finally, coherent population transfer between the inner and outer holes with attosecond pulse trains is discussed.
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| 8. |
- You, Jhih-An, et al.
(författare)
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Attosecond photoionization dynamics with stimulated core-valence transitions
- 2016
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 93:3
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Tidskriftsartikel (refereegranskat)abstract
- We investigate ionization of neon atoms by an isolated attosecond pump pulse in the presence of two coherent extreme ultraviolet or x-ray probe fields. The probe fields are tuned to a core-valence transition in the residual ion and induce spectral shearing of the photoelectron distributions. We show that the photoelectron-ion coincidence signal contains an interference pattern that depends on the temporal structure of the attosecond pump pulse and the stimulated core-valence transition. Many-body perturbation theory is used to compute atomic response times for the processes and we find strikingly different behavior for stimulation to the outer-core hole (2p <-> 2s) and stimulation to the inner-core hole (2p <-> 1s). The response time of the inner-core transition is found to be comparable to that of state-of-the-art laser-based characterization techniques for attosecond pulses.
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| 9. |
- Young, Linda, et al.
(författare)
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Roadmap of ultrafast x-ray atomic and molecular physics
- 2018
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3
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Forskningsöversikt (refereegranskat)abstract
- X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (1020 W cm-2) of x-rays at wavelengths down to ∼1 Ångstrom, and HHG provides unprecedented time resolution (∼50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ∼280 eV (44 Ångstroms) and the bond length in methane of ∼1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.
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| 10. |
- Zhang, Song Bin, et al.
(författare)
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Nonlinear resonant Auger spectroscopy in CO using an x-ray pump-control scheme
- 2016
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 94:6
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper we propose nonlinear femtosecond x-ray pump-probe spectroscopy to study the vibrational dynamics of a core-excited molecular state and discuss numerical results in CO. A femtosecond pump resonantly excites the carbon core-excited 1s-1π∗ state of the CO molecule. A second strong probe (control) pulse is applied at variable delay and is resonantly coupled to a valence excited state of the molecule. The strong nonlinear coupling of the control pulse induces Rabi flopping between the two electronic states. During this process, a vibrational wave packet in the core-excited state is created, which can be effectively manipulated by changing the time delay between pump and control pulses. We present an analysis of the resonant Auger electron spectrum and the transient absorption or emission spectrum on the pump transition and discuss their information content for reconstruction of the vibrational wave packet.
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