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Double Excitations in Helium Atoms and Lithium Compounds
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses the investigation of doubly excited 2l´nl states in helium atoms and double core excitations in solid lithium compounds.

Measurements on He are made in field free environments and under the influence of electric and magnetic fields, using synchrotron based inelastic photon scattering. Cross sections for scattering to singly excited final states are directly determined and compared to theoretical results and are found to be in excellent agreement. Radiative and spin-orbit effects are quantified and are shown to play an important role in the overall characterization of highly excited He states below the N =2 threshold. A dramatic electric field dependence is also observed in the flourecence yield already for relatively weak fields. This signal increase, induced by electric as well as magnetic fields, is interpreted in terms of mixing with states of higher fluorescence branching ratios.

Double core excitations at the lithium site in solid lithium compounds are investigated using resonant inelastic x-ray scattering (RIXS). The lithium halides LiF, LiCl, LiBr and LiI are studied as well as the molecular compounds Li2O, Li2CO3 and LiBF4. States with one, as well as both, of the excited electrons localized at the site of the bare lithium nucleus are identified, and transitions which involve additional band excitations are observed. A strong influence of the chemical surrounding is found, and it is discussed in terms of the ionic character of the chemical bond.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2006. , p. 114
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 186
Keywords [en]
Atomic and molecular physics, Soft X-ray emission, resonant inelastic X-ray scattering, double excitations, lithium halide, helium
Keywords [sv]
Atom- och molekylfysik
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-6889ISBN: 91-554-6572-2 (print)OAI: oai:DiVA.org:uu-6889DiVA, id: diva2:168397
Public defence
2006-05-26, Polhelmsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2016-04-21Bibliographically approved
List of papers
1. Resonant Inelastic Photon Scattering in Helium
Open this publication in new window or tab >>Resonant Inelastic Photon Scattering in Helium
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(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-94515 (URN)
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2012-10-09Bibliographically approved
2. Radiative and Relativistic Effects in the Decay of Highly Excited States in Helium
Open this publication in new window or tab >>Radiative and Relativistic Effects in the Decay of Highly Excited States in Helium
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2000 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 85, no 6, p. 1202-1205Article in journal (Refereed) Published
Abstract [en]

A recent experimental study [J.-E. Rubensson et al., Phys. Rev. Lett. 83, 947 (1999)] measured a significant fluorescence yield of the He( 2lnl) photoexcited resonances, showing major qualitative differences from nonrelativistic predictions. We present a further theoretical study of these states, and perform R-matrix multichannel quantum defect theory calculations to extract fluorescence and ionization cross sections. These theoretical results are in excellent agreement with newer, higher-resolution measurements. Radiative and spin-orbit effects are quantified and shown to play an important role in the overall characterization of highly excited states.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94516 (URN)10.1103/PhysRevLett.85.1202 (DOI)
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2017-12-14Bibliographically approved
3. Double Excitations of Helium in Weak Static Electric Fields
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2006 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, p. 043002-Article in journal (Refereed) Published
Abstract [en]

A dramatic electric field dependence has been observed in the fluorescence yield spectrum of the doubly excited states in helium, where a rich phenomenology is encountered below the N=2 threshold. Fluorescence yields of certain states can be tuned to zero, while other dipole-forbidden states are significantly enhanced, for fields much weaker than 1  kV/cm. Using an R-matrix multichannel quantum defect theory, spherical-to-parabolic frame transformation method, we are able to reproduce the main features of the observed spectrum, and we discuss the qualitative behavior in terms of weak electric field mixing.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94517 (URN)10.1103/PhysRevLett.96.043002 (DOI)
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2017-12-14Bibliographically approved
4. Magnetic-field induced enhancement in the fluorescence yield spectrum of doubly excited states in helium
Open this publication in new window or tab >>Magnetic-field induced enhancement in the fluorescence yield spectrum of doubly excited states in helium
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2006 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, no 25, p. 253002-Article in journal (Refereed) Published
Abstract [en]

An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity of the N=2 thresholds has been observed. The experimental results are in excellent agreement with predictions based on multichannel quantum defect theory, and it is demonstrated that the Rydberg electron ℓ mixing due to the diamagnetic interaction is essential for the description of the observed fluorescence yield intensity enhancement.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-95806 (URN)10.1103/PhysRevLett.97.253002 (DOI)000243414600018 ()
Available from: 2007-04-24 Created: 2007-04-24 Last updated: 2017-12-14
5. Resonant Inelastic Soft X-ray Scattering at Hollow Lithium States in Solid LiCl
Open this publication in new window or tab >>Resonant Inelastic Soft X-ray Scattering at Hollow Lithium States in Solid LiCl
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2004 (English)In: Physical Review Letters, Vol. 93, no 1, p. 016404-Article in journal (Refereed) Published
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94519 (URN)
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2016-04-26Bibliographically approved
6. Resonant inelastic soft x-ray scattering at double core excitations in solid LiCl
Open this publication in new window or tab >>Resonant inelastic soft x-ray scattering at double core excitations in solid LiCl
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2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, no 24, article id 245111Article in journal (Refereed) Published
Abstract [en]

Inelastic soft x-ray scattering in LiCl, resonantly enhanced at states with two Li 1s vacancies, is investigated. States in which both excited electrons are localized during the double core hole lifetime, in which one of the electrons delocalize, as well as triply excited states in which the double core excitation is accompanied by a valence-to-conduction band excitation, contribute to the scattering. The angular momentum symmetry of the involved states and the vibronic coupling during the scattering process are reflected in the angular anisotropy. The effect on the local electronic structure of multiple core holes is theoretically studied by means of supercell band calculations.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94520 (URN)10.1103/PhysRevB.73.245111 (DOI)000238696900035 ()
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2017-12-14Bibliographically approved
7. Double Core Excitations in Lithium Halides
Open this publication in new window or tab >>Double Core Excitations in Lithium Halides
2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 4, p. 045112-Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic x-ray scattering spectra of LiF , LiCl , LiBr , and LiI excited in the vicinity of the Li double core hole resonances are presented. All lithium halides show similar phenomenology, including scattering via states where both excited electrons are localized during the scattering process, as well as states where one electron delocalizes. Also transitions that involve additional band excitations are observed. A strong influence of the chemical surrounding is found, and it is discussed in terms of the ionic character of the chemical bond.

Keywords
X-ray scattering, Electron density of states and band structure of crystalline solids, Solid alkali halides
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94521 (URN)10.1103/PhysRevB.75.045112 (DOI)000243895600029 ()
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2017-12-14Bibliographically approved
8. Double Excitations at the Lithium Site in Solid Li Compounds
Open this publication in new window or tab >>Double Excitations at the Lithium Site in Solid Li Compounds
(English)Manuscript (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94522 (URN)
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2012-09-18Bibliographically approved
9. Multi-Center Resonant Inelastic Soft X-ray Scattering in LiI?
Open this publication in new window or tab >>Multi-Center Resonant Inelastic Soft X-ray Scattering in LiI?
(English)Manuscript (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-94523 (URN)
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2012-09-18Bibliographically approved

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