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Nuclear Dynamics in Linear and Non-linear X-ray Processes
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

New generations of brilliant synchrotron radiation sources and intense X-ray and optical lasers have opened unprecedent opportunities in linear and non-linear spectroscopies of molecules. This together with new instrumentation calls for further development of theory to explain observations and suggest new experiments. These two goals are the main objectives of the present thesis.

In the first part of the thesis we study resonant inelastic X-ray scattering of the oxygen molecule. Recent experimental data of O2 show the dependence of the vibrational profile on the polarization of the X-rays. This vibrational scattering anisotropy is explained by the interference of the resonant and nonresonant inelastic scattering channels in O2.

The second part of the thesis explores X-ray lasing caused by ultrafast dissociation of the HCl molecule in a repulsive core-excited state pumped by an X-ray free-electron laser. We show that the lasing efficiency is drastically enhanced due to the self-trapping of the amplified pulse into the ridge of the gain.

The third part of the thesis is devoted to another non-linear phenomenon - optical limiting. Our time-dependent simulations are in agreement with the experimental data and show that phthalocyanines with heavy central metals exhibit good optical limiting properties for nanosecond pulses.

Symmetry and the symmetry breaking are important fundamental concepts in physics, chemistry and biology. In the next part of the thesis we study theoretically the novel symmetry breaking mechanism in resonant Auger scattering. Both theory and electron-ion coincidence measurements for the oxygen molecule evidence the symmetry breaking of the oxygen cation caused by momentum exchange between the fast Auger electron and counter propagating dissociating oxygen atoms.

The last part of the thesis is devoted to the role of the rotational degrees of freedom in X- ray ionization of molecules. We present here new results related to the rotational Doppler and angular recoil effects in X-ray ionization using the N2 and HCl molecules as illustrating examples. The dependence of the ionization cross section on the direction of ejection of fast electrons explains the sensitivity of the rotational broadening to the final state and to the polarization of X-rays observed recently for the N2 molecule. The theory reveals the novel effect of site-selectivity of X-ray valence ionization caused by the excitation of the rotational degrees of freedom which is different for different ionization sites. Large recoil angular momentum related to the ejection of an electron from the light hydrogen atom results in a red shifted broad pedestal in the X-ray photoelectron spectrum of HCl.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , viii, 62 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2013:15
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-133432ISBN: 978-91-7501-859-1 (print)OAI: oai:DiVA.org:kth-133432DiVA: diva2:661197
Public defence
2013-12-13, FA32, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20131108

Available from: 2013-11-08 Created: 2013-10-31 Last updated: 2013-11-08Bibliographically approved
List of papers
1. Interference between Resonant and Nonresonant Inelastic X-Ray Scattering
Open this publication in new window or tab >>Interference between Resonant and Nonresonant Inelastic X-Ray Scattering
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2013 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 22, 223001- p.Article in journal (Refereed) Published
Abstract [en]

A detailed study of inelastic x-ray scattering from the ground state to the Σg3(3σg-13sg1) state of the O2 molecule is presented. The observed angular anisotropy shows that the vibrational excitations within this final state are strongly dependent on the polarization of the incident radiation. The analysis demonstrates that this is a manifestation of interference between resonant and direct nonresonant inelastic x-ray scattering. This interference provides a new tool to monitor nuclear dynamics by relative rotation of the polarization vectors of the incident and scattered photons.

Keyword
inelastic X-ray scattering, nuclear dynamics, scattering anisotropy
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-133423 (URN)10.1103/PhysRevLett.110.223001 (DOI)000319682200009 ()2-s2.0-84878373055 (Scopus ID)
Note

QC 20131106

Available from: 2013-11-01 Created: 2013-10-31 Last updated: 2017-12-06Bibliographically approved
2. Dissociative X-ray Lasing
Open this publication in new window or tab >>Dissociative X-ray Lasing
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2012 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 23, 233905- p.Article in journal (Refereed) Published
Abstract [en]

X-ray lasing is predicted to ensue when molecules are pumped into dissociative core-excited states by a free-electron-laser pulse. The lasing is due to the population inversion created in the neutral dissociation product, and the process features self-trapping of the x-ray pulse at the gain ridge. Simulations performed for the HCl molecule pumped at the 2p(1/2) -> 6 sigma resonance demonstrate that the scheme can be used to create ultrashort coherent x-ray pulses.

Keyword
Coherent X-rays, Core-excited state, Dissociation products, Population inversions, Self-trapping, X ray pulse
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-109612 (URN)10.1103/PhysRevLett.109.233905 (DOI)000312012200017 ()2-s2.0-84870600813 (Scopus ID)
Funder
Swedish Research CouncilSwedish e‐Science Research Center
Available from: 2013-01-08 Created: 2013-01-08 Last updated: 2017-12-06Bibliographically approved
3. Numerical analysis on optical limiting performance of a series of phthalocyanines for nanosecond pulses
Open this publication in new window or tab >>Numerical analysis on optical limiting performance of a series of phthalocyanines for nanosecond pulses
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2012 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 45, no 8, 085402- p.Article in journal (Refereed) Published
Abstract [en]

The optical limiting properties of a series of peripherally substituted phthalocyanines with different central metals and axial chloride ligand for nanosecond pulses have been studied by solving numerically the two-dimensional paraxial field equation together with the rate equations using the Crank-Nicholson method. It is shown that all of these compounds exhibit good optical limiting behaviour, and phthalocyanines with heavier central metals have better optical limiting performance due to the faster intersystem crossing caused by the enhanced spin-orbit coupling. The major mechanism of optical limiting for long pulses is the sequential (singlet-singlet)x( triplet-triplet) nonlinear absorption. Dynamics of populations is characterized mainly by the effective transfer time of the population from the ground state to the lowest triplet state. The long lifetime of the triplet state is important but not determinant. In addition, the performance of optical limiting strongly depends on the thickness and concentration of the absorber.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-94039 (URN)10.1088/0953-4075/45/8/085402 (DOI)000302778700018 ()2-s2.0-84859589860 (Scopus ID)
Note
QC 20120507Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2017-12-07Bibliographically approved
4. Symmetry breaking by site-dependent momentum exchange
Open this publication in new window or tab >>Symmetry breaking by site-dependent momentum exchange
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(English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, ISSN 1745-2473Article in journal (Other academic) Submitted
Keyword
symmetry breaking, momentum exchange, Young's double-slit interference, Doppler effect
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-133429 (URN)
Note

QS 2013

Available from: 2013-11-01 Created: 2013-10-31 Last updated: 2017-12-06Bibliographically approved
5. Rotational Doppler effect: a probe for molecular anisotropy
Open this publication in new window or tab >>Rotational Doppler effect: a probe for molecular anisotropy
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(English)Manuscript (preprint) (Other academic)
Keyword
rotational Doppler effect, molecular anisotropy, X-ray photoelectron spectra
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-133430 (URN)
Note

QS 2013

Available from: 2013-11-01 Created: 2013-10-31 Last updated: 2016-10-17Bibliographically approved
6. Site-selective photoemission from delocalized valence shells: the role of molecular rotation
Open this publication in new window or tab >>Site-selective photoemission from delocalized valence shells: the role of molecular rotation
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(English)Manuscript (preprint) (Other academic)
Keyword
site selectivity, rotational Doppler effect, recoil effext, X-ray photoionization
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-133431 (URN)
Note

QS 2013

Available from: 2013-11-01 Created: 2013-10-31 Last updated: 2013-11-08Bibliographically approved

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