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Spontaneous and stimulated X-ray Raman scattering
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis is devoted to theoretical studies of resonant X-ray scattering and propagation of strong X-ray pulses. In the first part of the thesis the nuclear dynamics of different molecules is studied using resonant X-ray Raman and resonant Auger scattering techniques. We show that the shortening of the scattering duration by the detuning results in a purification of the Raman spectra from overtones and soft vibrational modes. The simulations are in a good agreement with measurements, performed at the MAX-II and the Swiss Light Source with vibrational resolution. We explain why the scattering to the ground state nicely displays the vibrational structure of liquid acetone in contrast to excited final state. Theory of resonant X-ray scattering by liquids is developed. We show that, contrary to aqueous acetone, the environmental broadening in pure liquid acetone is twice smaller than the broadening by soft vibrational modes significantly populated at room temperature. Similar to acetone, the "elastic" band of X-ray Raman spectra of molecular oxygen is strongly affected by the Thomson scattering. The Raman spectrum demonstrates spatial quantum beats caused by two interfering wave packets with different momenta as the oxygen atoms separate. It is found that the vibrational scattering anisotropy caused by the interference of the "inelastic" Thomson and resonant scattering channels in O2. A new spin selection rule is established in inelastic X-ray Raman spectra of O2. It is shown that the breakdown of the symmetry selection rule based on the parity of the core hole, as the core hole and excited electron swap parity. Multimode calculations explain the two thresholds of formation of the resonant Auger spectra of the ethene molecule by the double-edge structure of absorption spectrum caused by the out-of- and in-plane modes. We predict the rotational Doppler effect and related broadening of X-ray photoelectron and resonant Auger spectra, which has the same magnitude as its counterpart-the translational Doppler effect. The second part of the thesis explores the interaction of the medium with strong X-ray free-electron laser (XFEL) fields. We perform simulations of nonlinear propagation of femtosecond XFEL pulses in atomic vapors by solving coupled Maxwell's and density matrix equations. We show that self-seeded stimulated X-ray Raman scattering strongly influences the temporal and spectral structure of the XFEL pulse. The generation of Stokes and four-wave mixing fields starts from the seed field created during pulse propagation due to the formation of extensive ringing pattern with long spectral tail. We demonstrate a compression into the attosecond region and a slowdown of the XFEL pulse up to two orders of magnitude. In the course of pulse propagation, the Auger yield is strongly suppressed due to the competitive channel of stimulated emission. We predict a strong X-ray fluorescence from the two-core-hole states of Ne created in the course of the two-photon X-ray absorption.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , viii, 71 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2011:8
Keyword [en]
resonant X-ray scattering, resonant Auger scattering, rotational Doppler broadening, XFEL pulse
National Category
Atom and Molecular Physics and Optics Analytical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-32859ISBN: 978-91-7415-925-7OAI: oai:DiVA.org:kth-32859DiVA: diva2:412253
Public defence
2011-05-13, FA32, AlbaNova, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110426Available from: 2011-04-26 Created: 2011-04-21 Last updated: 2011-11-23Bibliographically approved
List of papers
1. Shortening scattering duration by detuning purifies Raman spectra of complex systems
Open this publication in new window or tab >>Shortening scattering duration by detuning purifies Raman spectra of complex systems
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2011 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 511, no 1-3, 16-21 p.Article in journal (Refereed) Published
Abstract [en]

We highlight Resonant Raman scattering as a dynamical process with a finite duration time that results from not only the irreversible homogeneous broadening but also the reversible dephasing caused by the detuning from the resonance, which acts as a camera shutter with a regulated scattering duration. This provides a practical tool of controlling the scattering time. We show that the typical dephasing rates in gas and condensed matter phases are not sufficiently high to make the scattering fast. The detuning from the resonance leads to a strong purification of Raman spectrum from the contamination by higher overtones and soft modes.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-32861 (URN)10.1016/j.cplett.2011.05.064 (DOI)000292687900004 ()2-s2.0-79960281505 (ScopusID)
Funder
Swedish e‐Science Research Center
Note
Updated from manuscript to article in journal 20110802Available from: 2011-04-21 Created: 2011-04-21 Last updated: 2012-05-24Bibliographically approved
2. Intramolecular soft modes and intermolecular interactions in liquid acetone
Open this publication in new window or tab >>Intramolecular soft modes and intermolecular interactions in liquid acetone
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2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 13, 132202- p.Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic x-ray scattering spectra excited at the O1s(-1)pi* resonance of liquid acetone are presented. Scattering to the electronic ground state shows a resolved vibrational progression where the dominant contribution is due to the C-O stretching mode, thus demonstrating a unique sensitivity of the method to the local potential energy surface in complex molecular systems. For scattering to electronically excited states, soft vibrational modes and, to a smaller extent, intermolecular interactions give a broadening, which blurs the vibrational fine structure. It is predicted that environmental broadening is dominant in aqueous acetone.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-48513 (URN)10.1103/PhysRevB.84.132202 (DOI)000296372300001 ()2-s2.0-80155152537 (ScopusID)
Funder
Swedish Research Council
Note
QC 20111123 Uppdaterat från ManuskriptAvailable from: 2011-11-23 Created: 2011-11-21 Last updated: 2011-11-23Bibliographically approved
3. Spatial Quantum Beats in Vibrational Resonant Inelastic Soft X-Ray Scattering at Dissociating States in Oxygen
Open this publication in new window or tab >>Spatial Quantum Beats in Vibrational Resonant Inelastic Soft X-Ray Scattering at Dissociating States in Oxygen
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2011 (English)In: Physical Review Letters, ISSN 0031-9007, Vol. 106, 153004-153008 p.Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic soft x-ray scattering (RIXS) spectra excited at the 1σg→3σu resonance in gas-phase O2 show excitations due to the nuclear degrees of freedom with up to 35 well-resolved discrete vibronic states and a continuum due to the kinetic energy distribution of the separated atoms. The RIXS profile demonstrates spatial quantum beats caused by two interfering wave packets with different momenta as the atoms separate. Thomson scattering strongly affects both the spectral profile and the scattering anisotropy.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-32876 (URN)10.1103/PhysRevLett.106.153004 (DOI)000289525300005 ()2-s2.0-79960623604 (ScopusID)
Funder
Swedish e‐Science Research Center
Note
QC 20110426 QC 20110512Available from: 2011-04-26 Created: 2011-04-26 Last updated: 2012-05-24Bibliographically approved
4. Hidden symmetry in molecular oxygen
Open this publication in new window or tab >>Hidden symmetry in molecular oxygen
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(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-32864 (URN)
Note
QC 20110426Available from: 2011-04-21 Created: 2011-04-21 Last updated: 2011-04-26Bibliographically approved
5. Multimode Resonant Auger Scattering from the Ethene Molecule
Open this publication in new window or tab >>Multimode Resonant Auger Scattering from the Ethene Molecule
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2011 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 115, no 18, 5103-5112 p.Article in journal (Refereed) Published
Abstract [en]

Resonant Auger spectra of ethene molecule have been measured with vibrational resolution at several excitation energies in the region of the C1s(-1)1b(2g)(π*) resonance. The main features observed in the experiment have been assigned and are accurately interpreted on the basis of ab initio multimode calculations. Theory explains the extended vibrational distribution of the resonant Auger spectra and its evolution as a function of the excitation energy by multimode excitation during the scattering process. As a result, the resonant Auger spectra display two qualitatively different spectral features following the Raman and non-Raman dispersion laws, respectively. Calculations show that two observed thresholds of formation of non-Raman spectral bands are related to the "double-edge" structure of the X-ray absorption spectrum.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-32890 (URN)10.1021/jp104228x (DOI)000290127100006 ()21370829 (PubMedID)2-s2.0-79958238236 (ScopusID)
Note
QC 20110426 QC 20110609Available from: 2011-04-26 Created: 2011-04-26 Last updated: 2016-10-13Bibliographically approved
6. Rotational Doppler effect in x-ray photoionization
Open this publication in new window or tab >>Rotational Doppler effect in x-ray photoionization
2010 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 5, 052506- p.Article in journal (Refereed) Published
Abstract [en]

The energy of the photoelectron experiences a red or blue Doppler shift when the molecule recedes from the detector or approaches him. This results in a broadening of the photoelectron line due to the translational thermal motion. However, the molecules also have rotational degrees of freedom and we show that the translational Doppler effect has its rotational counterpart. This rotational Doppler effect leads to an additional broadening of the spectral line of the same magnitude as the Doppler broadening caused by translational thermal motion. The rotational Doppler broadening as well as the rotational recoil broadening is sensitive to the molecular orbital from which the photoelectron is ejected. This broadening should be taken into account in analysis of x-ray photoemission spectra of super-high resolution and it can be directly observed using x-ray pump-probe spectroscopy.

Keyword
FREE-ELECTRON LASER, PHOTOELECTRON-SPECTROSCOPY, RAMAN-SCATTERING, FINE-STRUCTURE, DISTRIBUTIONS, INTERFERENCE, DEPENDENCE, RADIATION, THRESHOLD, SPECTRA
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-27055 (URN)10.1103/PhysRevA.82.052506 (DOI)000284044500004 ()2-s2.0-78649588474 (ScopusID)
Note
QC 20101213Available from: 2010-12-13 Created: 2010-12-06 Last updated: 2011-04-26Bibliographically approved
7. Propagation of a strong x-ray pulse: Pulse compression, stimulated Raman scattering, amplified spontaneous emission, lasing without inversion, and four-wave mixing
Open this publication in new window or tab >>Propagation of a strong x-ray pulse: Pulse compression, stimulated Raman scattering, amplified spontaneous emission, lasing without inversion, and four-wave mixing
2010 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 81, no 1Article in journal (Refereed) Published
Abstract [en]

We study the compression of strong x-ray pulses from x-ray free-electron lasers (XFELs) propagating through the resonant medium of atomic argon. The simulations are based on the three-level model with the frequency of the incident x-ray pulse tuned in the 2p(3/2)-4s resonance. The pulse propagation is accompanied by the self-seeded stimulated resonant Raman scattering (SRRS). The SRRS starts from two channels of amplified spontaneous emission (ASE), 4s-2p(3/2) and 3s-2p(3/2), which form the extensive ringing pattern and widen the power spectrum. The produced seed field triggers the Stokes ASE channel 3s-2p(3/2). The population inversion is quenched for longer propagation distances where the ASE is followed by the lasing without inversion (LWI), which amplifies the Stokes component. Both ASE and LWI reshape the input pulse: The compressed front part of the pulse (up to 100 as) is followed by the long tail of the ringing and beating between the pump and Stokes frequencies. The pump pulse also generates weaker Stokes and anti-Stokes fields caused by four-wave mixing. These four spectral bands have fine structures caused by the dynamical Stark effect. A slowdown of the XFEL pulse up to 78% of the speed of light in vacuum is found because of a large nonlinear refractive index.

Keyword
free-electron laser, light-pulses, spectroscopy, bandwidth, edge, fel, ar
National Category
Atom and Molecular Physics and Optics Atom and Molecular Physics and Optics Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-19155 (URN)10.1103/PhysRevA.81.013812 (DOI)000274001500137 ()2-s2.0-74949113283 (ScopusID)
Funder
Swedish Research Council
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2016-05-23Bibliographically approved
8. Slowdown and compression of a strong X-ray free-electron pulse propagating through the Mg vapors
Open this publication in new window or tab >>Slowdown and compression of a strong X-ray free-electron pulse propagating through the Mg vapors
2009 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 87, no 6Article in journal (Refereed) Published
Abstract [en]

Here we study the propagation of a strong X-ray free-electron pulse through the resonant medium of atomic Mg accompanied by the self-seeded stimulated resonant X-ray Raman scattering. The X-ray pulse is decelerated by two orders of magnitude because of nonlinear interaction and experiences a 6-fold compression. The simulations are based on a strict numerical solution of the coupled Bloch and Maxwell equations for a 50 fs pulse tuned in the 2p(3/2)-4s resonance (54.8 eV). The extensive ringing tail produced during propagation widens the power spectrum. This seed field triggers the Stokes channel 3s-2p(3/2) (49.4 eV) of stimulated resonant X-ray Raman scattering and the weaker Stokes and anti-Stokes fields caused by four-wave mixing. The beating between the Stokes and pump fields quenches the population inversion at longer propagation distances where lasing without inversion enhances the Stokes component.

Identifiers
urn:nbn:se:kth:diva-18854 (URN)10.1209/0295-5075/87/64002 (DOI)000270659600014 ()2-s2.0-78650936875 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-04-26Bibliographically approved
9. Auger effect in the presence of strong x-ray pulses
Open this publication in new window or tab >>Auger effect in the presence of strong x-ray pulses
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2010 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, ISSN 1050-2947, Vol. 81, no 4, 043412- p.Article in journal (Refereed) Published
Abstract [en]

We study the role of propagation of strong x-ray free-electron laser pulses on the Auger effect. When the system is exposed to a strong x-ray pulse the stimulated emission starts to compete with the Auger decay. As an illustration we present numerical results for Ar gas with the frequency of the incident x-ray pulse tuned in the 2p(3/2)-4s resonance. It is shown that the pulse propagation is accompanied by two channels of amplified spontaneous emission, 4s-2p(3/2) and 3s-2p(3/2), which reshape the pulse when the system is inverted. The population inversion is quenched for longer propagation distances where lasing without inversion enhances the Stokes component. The results of simulations show that the propagation of the strong x-ray pulses affect intensively the Auger branching ratio.

Keyword
Amplified spontaneous emissions, Auger decays, Auger effects, Branching ratio, Lasing without inversion, Numerical results, Population inversions, Propagation distances, Pulse propagation, Stokes component, Two channel, X ray pulse, X-ray free electron lasers
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-14258 (URN)10.1103/PhysRevA.81.043412 (DOI)000277227300128 ()2-s2.0-77951125476 (ScopusID)
Funder
Swedish Research CouncilCarl Tryggers foundation
Note

QC 20100728

Available from: 2010-07-28 Created: 2010-07-28 Last updated: 2014-04-11Bibliographically approved
10. Two-photon-induced x-ray emission in neon atoms
Open this publication in new window or tab >>Two-photon-induced x-ray emission in neon atoms
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2010 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 4, 043430- p.Article in journal (Refereed) Published
Abstract [en]

We investigated the resonant x-ray emission from a neon atom induced by the two-photon population of a double-core-hole excited state. Two qualitatively different schemes of this process are studied: The first one involves an off-resonant intermediate single-core-hole state; the second scheme passes through a resonant core-ionized intermediate state. The numerical simulations of the resonant x-ray emission performed for different peak intensities and pulse durations show significant population of the double-core-hole final states. Therefore, rather strong two-photon absorption-induced x-ray emission is predicted for both studied schemes. Thus, high counting rates in experimental measurements are expected.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-26221 (URN)10.1103/PhysRevA.82.043430 (DOI)000283416300007 ()2-s2.0-78650962134 (ScopusID)
Funder
Swedish e‐Science Research Center
Note
QC 20110222Available from: 2011-02-22 Created: 2010-11-21 Last updated: 2012-05-22Bibliographically approved

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