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Nuclear Dynamics in X-ray Absorption and Raman Scattering
KTH, School of Biotechnology (BIO).
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents theoretical studies of several x-ray spectroscopies - x-ray absorption, x-ray photoelectron emission, radiative and non-radiative resonant Raman scattering spectroscopy. The main focus point is investigating the influence of nuclear dynamics on these spectra for a variety of small molecules - naphthalene, biphenyl, ethylene, the water dimer, HCl, CO. The theoretical tools used consist of the basic equations of the relevant x-ray spectroscopy. Wave packet methods are also used. The molecular parameters needed for our simulations are obtained through suitable quantum chemical calculations, based on either wave function or density functional methods. Our simulations are compared to experimental data, where available.

Simulations of x-ray absorption and x-ray photoionization spectra for naphthalene and biphenyl show that the spectral shapes are heavily influenced by the joint effect of two factors -- chemical shifts and excitations of vibrational progression. Comparison between the two molecules and also comparison to a reference case -- benzene, provides useful insight into the molecular behavior under core excitation.

In a further step, we consider the O1s x-ray photoelectron spectrum of the water dimer. A substantial broadening of the two bands originating from the donor and the acceptor oxygen is found. It is caused by excitations of soft intermolecular vibrational modes, associated with the hydrogen bond.

Another strong influence of the nuclear dynamics is clearly seen in the resonant x-ray Raman scattering of HCl. Vibrational collapse is observed experimentally and confirmed theoretically for distinctive situations. This effect allows to eliminate completely the vibrational broadening, and hence, considerably increase the spectral resolution.

We considered also the vibrational dynamics in resonant soft x-ray Raman scattering from ethylene. The importance of vibronic coupling and symmetry effects is discussed and emphasized. We obtained excellent agreement with the experimental data.

We predict an interference effect in the resonant Auger scattering from fixed-in-space molecules. By exciting a molecule to a dissociative state and measuring the angular distribution of the Auger electrons in coincidence with the molecular ion, one can observe this effect. The interference pattern can be used after Fourier transformation for extracting structural data about the studied system.

We have found that two-center interference leads to an enhancement of the recoil effect.

Finally, it is shown that core excitation to doubly-excited dissociative Pi state is accompanied by Doppler splitting of the atomic peak in resonant Auger scattering from carbon monoxide.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , viii, 57 p.
Series
Theses in philosophy from the Royal Institute of Technology, ISSN 1650-8831
Keyword [en]
x-ray scattering, theory, simulations, recoil, Doppler effect, nuclear dynamics, Auger, XPS
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-3902ISBN: 91-7178-276-1 (print)OAI: oai:DiVA.org:kth-3902DiVA: diva2:9960
Public defence
2006-04-21, FA 32, AlbaNova, Roslagstullsbacken 21, 09:00
Opponent
Supervisors
Note
QC 20100910Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-09-10Bibliographically approved
List of papers
1. Core-excitations of naphthalene: Vibrational structure versus chemical shifts
Open this publication in new window or tab >>Core-excitations of naphthalene: Vibrational structure versus chemical shifts
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2004 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, no 12, 5733-5739 p.Article in journal (Refereed) Published
Abstract [en]

The initial state chemical shifts and vibrational fine structure of core excitations of naphthalene were analyzed using high-resolution x-ray photoelectron emission (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectra. The carbon atoms at peripheral sites were found to experience a small chemical shift and exhibit similar charge-vibrational coupling. The C-H stretching modes provide significant contributions to overall shape of spectra in the XPS spectra. The results show that vibrational fine structure dominates by particular C-C stretching modes, and in XPS of C2 and C3 sites also by high-energy C-H stretching modes.

Keyword
Approximation theory, Carbon, Carrier concentration, Electron transitions, Harmonic analysis, Kinetic energy, Mathematical models, Molecular dynamics, Molecular vibrations, Photoemission, Photoionization, Relaxation processes, X ray photoelectron spectroscopy
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5551 (URN)10.1063/1.1784450 (DOI)000223872000020 ()2-s2.0-5444257939 (Scopus ID)
Note
QC 20100906 20110916Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
2. Core-excitations of biphenyl
Open this publication in new window or tab >>Core-excitations of biphenyl
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2005 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 109, no 7, 1330-1336 p.Article in journal (Refereed) Published
Abstract [en]

High-resolution C(1s) near-edge X-ray absorption and X-ray photoionization spectra of the free biphenyl molecule are presented and theoretically analyzed in order to allow an assignment of the observed spectral features. Finite lifetime broadening, a high density of vibrational states, and a strong overlap of contributions from chemically different carbon atom sites only partially allow resolving the vibrational fine structure. However, the shape and width of the spectral profiles are strongly determined by both chemical shifts and vibronic effects. In particular, different from photoionization of valence levels, both types of core level spectra do not contain contributions from dihedral modes which are related to the twisting motion of the two phenyl rings. Contrary to naphthalene, C-H stretching modes are significantly enhanced in the core excitation spectra of biphenyl while the contributions from C-C stretching modes are reduced.

Keyword
Absorption spectroscopy, Chemical bonds, Computer simulation, Crucibles, Differentiation (calculus), Electron energy levels, Molecular vibrations, Oligomers, Oscillators (electronic), Photoionization, Resonance, X ray photoelectron spectroscopy
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5552 (URN)10.1021/jp045447z (DOI)000227108500010 ()2-s2.0-14644427195 (Scopus ID)
Note
QC 20100906Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
3. A theoretical study of the role of the hydrogen bond on core ionization of the water dimer
Open this publication in new window or tab >>A theoretical study of the role of the hydrogen bond on core ionization of the water dimer
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2005 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 312, no 1-3, 311-318 p.Article in journal (Refereed) Published
Abstract [en]

Motivated by the interest in using X-ray spectra for probing of hydrogen bonded networks we developed a quantum model for simulations of the electronic-vibrational profile of the X-ray core photoelectron spectrum of the water dimer. It is found that the potential surfaces of the donor and acceptor O1s core-ionized states of this system display a qualitative difference. Large gradients of the potential in the core ionized state along some intermolecular coordinates combined with small vibrational frequencies breaks down completely the harmonic approximation. The band profiles are therefore treated using a quasi-continuum approximation. The weak hydrogen bonding and the drastic change of water dimer potential under core ionization is responsible for the anomalously strong vibrational broadening: 0.4 eV for the acceptor band and 0.6 eV for the donor band. The core ionization of the donor oxygen is accompanied by proton transfer which should be observable in X-ray fluorescence or Auger spectra.

Place, publisher, year, edition, pages
Elsevier, 2005
Keyword
X-ray photoionization, hydrogen bonding
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5553 (URN)10.1016/j.chemphys.2004.12.006 (DOI)000228206700033 ()2-s2.0-15744404650 (Scopus ID)
Note

QC 20100825

Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
4. Femtosecond nuclear motion of HCl probed by resonant x-ray Raman scattering in the Cl 1s region
Open this publication in new window or tab >>Femtosecond nuclear motion of HCl probed by resonant x-ray Raman scattering in the Cl 1s region
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2006 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 73, no 2, 020706(R)- p.Article in journal (Refereed) Published
Abstract [en]

Femtosecond dynamics are observed by resonant x-ray Raman scattering (RXS) after excitation along the dissociative Cl 1s -> 6 sigma(*) resonance of gas-phase HCl. The short core-hole lifetime results in a complete breakdown of the common nondispersive behavior of soft-x-ray transitions between parallel potentials. We evidence a general phenomenon of RXS in the hard-x-ray region: a complete quenching of vibrational broadening. This opens up a unique opportunity for superhigh resolution x-ray spectroscopy beyond vibrational and lifetime limitations.

Keyword
fast dissociation, decay, spectroscopy, molecules, excitation, dynamics, states
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5554 (URN)10.1103/PhysRevA.73.020706 (DOI)000235668100009 ()2-s2.0-33644520618 (Scopus ID)
Note
QC 20100910Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
5. Non-Adiabatic effects in Resonant Inelastic x-ray Scattering
Open this publication in new window or tab >>Non-Adiabatic effects in Resonant Inelastic x-ray Scattering
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2005 (English)In: Physical Review Letters, ISSN 0031-9007, Vol. 95, no 16, 163002- p.Article in journal (Refereed) Published
Abstract [en]

We have studied the spectral features of resonant inelastic x-ray scattering of condensed ethylene with vibrational selectivity both experimentally and theoretically. Purely vibrational spectral loss features and coupled electronic and vibrational losses are observed. The one-step theory for resonant soft x-ray scattering is applied, taking multiple vibrational modes and vibronic coupling into account. Our investigation of ethylene underlines that the assignment of spectral features observed in resonant inelastic x-ray scattering of polyatomic systems requires an explicit description of the coupled electronic and vibrational loss features.

Keyword
Nonadiabatic effects; Resonant inelastic X-ray scattering; Vibrational spectral loss; Energy dissipation; Ethylene; Resonance
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-6998 (URN)10.1103/PhysRevLett.95.163002 (DOI)000232558400019 ()2-s2.0-28844452203 (Scopus ID)
Note
QC 20100813Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-09-10Bibliographically approved
6. Interchannel interference in resonant Auger scattering from fixed-in-space molecules as a technique for structure determination
Open this publication in new window or tab >>Interchannel interference in resonant Auger scattering from fixed-in-space molecules as a technique for structure determination
2004 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 70, no 3, 032507- p.Article in journal (Refereed) Published
Abstract [en]

A method for structure determination of polyatomic molecules with equivalent atoms is suggested. The method is based on an interference pattern in the resonant Auger scattering process. This pattern is caused by interference of resonant Auger channels corresponding to a core hole localized on different equivalent atoms. The predicted effect can be observed in angular resolved electron-ion coincidence measurements or, alternatively, using the ordinary Auger technique on surface-oriented molecules.

Keyword
ray raman-scattering, k-edge spectra, angular-distribution, high-resolution, decay, o2, dissociation, electrons, n2
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-23820 (URN)10.1103/PhysRevA.70.032507 (DOI)000224623000065 ()2-s2.0-19644400661 (Scopus ID)
Note
QC 20100525 QC 20110923Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
7. Role of the recoil effect on two-center interference in x-ray photoionization
Open this publication in new window or tab >>Role of the recoil effect on two-center interference in x-ray photoionization
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2006 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 329, no 1-3, 329-337 p.Article in journal (Refereed) Published
Abstract [en]

X-ray photoelectron spectra of the N-2 molecule are studied both experimentally and theoretically in the extended energy region up to 1 keV. The ratio of the photoionization cross sections for the gerade and ungerade core levels displays a modulation in the high energy region caused by the two-center interference, as predicted by Cohen and Fano (CF) in 1966. The physical background of this CF effect is the same as in Young's double-slit experiment. We have found that the interference pattern deviates significantly from the CF prediction. The origin of such a breakdown of the CF formula is the scattering of the photoelectron inside the molecule and the momentum transfer from the emitted fast photoelectron to the nuclei. Usually the recoil effect is small. We show that the electron recoil strongly affects the two-center interference pattern. Both stationary and dynamical aspects of the recoil effect shed light on the role of the momentum exchange in the two-center interference.

Keyword
X-ray photoelectron spectroscopy, recoil, interference
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5557 (URN)10.1016/j.chemphys.2006.06.022 (DOI)000241574500035 ()2-s2.0-33749537232 (Scopus ID)
Note

Uppdaterad från manuskript till artikel: 20100910 Tidigare titel: Role of the recoil effect on two-center interference in x-ray photoionization of N$_2$ molecules QC 20100910

Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
8. Electronic Doppler effect in resonant Auger decay of CO molecules upon excitation near a shake-up Pi resonance
Open this publication in new window or tab >>Electronic Doppler effect in resonant Auger decay of CO molecules upon excitation near a shake-up Pi resonance
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2007 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 062704Article in journal (Refereed) Published
Abstract [en]

Wepresent an experimental observation of the electronic Doppler effect inresonant Auger spectra upon core excitation slightly above the carbonK edge of the CO molecule. Thus the electronic Dopplereffect has been identified in above-threshold excitation, and in atransition of symmetry. Ab initio calculations of the potentialenergy curves of the relevant states of CO and thewave packet technique have been employed to provide a theoreticalbackground to the experimental studies. The weak feature around 299.4  eVin the photoabsorption spectrum, whose decay has been investigated bythe present experiment, is assigned to double (core-valence) excitations toC 1s shake-up states |1s1−1*2 with a strong dissociative character,and the Doppler splitting of the atomic peak has beenreproduced by the simulation.

Place, publisher, year, edition, pages
APS, 2007
Keyword
ray raman-scattering, photochemistry beamline bl27su, excited-states, shell, photoemission, radiation, dynamics, autoionization, dissociation, spectroscopy
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-9733 (URN)10.1103/PhysRevA.76.062704 (DOI)000251985900062 ()2-s2.0-37249052816 (Scopus ID)
Note

Uppdaterad från manuskript till artikel: 20100910 QC 20100910

Available from: 2008-12-04 Created: 2008-12-04 Last updated: 2016-05-18Bibliographically approved

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