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Transition Properties of f-electrons in Rare-earth Optical Materials
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main purpose of this thesis is to theoretically study energy levels and intra-electronic transition intensities for various f-electron systems. The f-f electronic dipole transitions are parity-forbidden for a free ion but become non-zero when the ion is subject to a crystal-field. This is commonly described within the framework of Judd-Ofelt theory which accounts for the mixing of odd parity into the wave-functions.

Some refinements and quantitative studies have been made by applying many-body perturbation theory, or the perturbed functions approach, to obtain effective dipole operators due to correlation, spin-orbit and higher order crystal-field effects not included in Judd-Ofelt theory. A software for the computation of f-electron multiplets and Stark levels was implemented and published as well.

The single- and pair-functions used for the evaluation of intensity parameters were obtained by solving various inhomogeneous Schrödinger equations. The wave-functions and energies obtained by diagonalizing an effective Hamiltonian have been used together with the oscillator strength methods to simulate absorption spectrum. Consistent crystal-field parameters applied in some of the papers were obtained by fitting crystal polarizabilities to reflect the experimental Stark levels. The same crystal model was then used to generate odd crystal field parameters needed for the f-f transition intensities. The total effect of these refinements are spectral features that usually agree well with experimental findings. Some of these methods have also been applied and seen to be quite useful for the understanding of optical fiber amplifiers frequently used in today's optical networks.

Finally, a finite-difference approach was applied for the Helium iso-electronic sequence. The exact wave-function was expanded in a sum of partial waves, and accurate ground- and excited state energies were obtained by using the iterative Arnoldi approach.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2004. , p. 50
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 944
Keywords [en]
Physics, rare-earth ions, oscillator strengths, correlation, crystal field, f-electrons
Keywords [sv]
Fysik
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-4014ISBN: 91-554-5890-4 (print)OAI: oai:DiVA.org:uu-4014DiVA, id: diva2:164146
Public defence
2004-03-19, Siegbahnsalen, Ångström laboratory, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 14:00
Opponent
Supervisors
Available from: 2004-02-25 Created: 2004-02-25 Last updated: 2012-04-04Bibliographically approved
List of papers
1. The energy matrix using determinantal product states applied to Ho:YAG
Open this publication in new window or tab >>The energy matrix using determinantal product states applied to Ho:YAG
2000 In: J. Alloys Compd., ISSN 0925-8388, Vol. 303, p. 280-284Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91417 (URN)
Available from: 2004-02-25 Created: 2004-02-25Bibliographically approved
2. The crystal dependent open-shell polarizability of f-elements: higher order contributions
Open this publication in new window or tab >>The crystal dependent open-shell polarizability of f-elements: higher order contributions
2000 In: J. Alloys Compd., ISSN 0925-8388, Vol. 303, p. 345-348Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91418 (URN)
Available from: 2004-02-25 Created: 2004-02-25Bibliographically approved
3. An atomic program for energy levels of equivalent electrons: lanthanides and actinides
Open this publication in new window or tab >>An atomic program for energy levels of equivalent electrons: lanthanides and actinides
2001 In: Comput. Phys. Commun., ISSN 0010-4755, Vol. 133, p. 396-406Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91419 (URN)
Available from: 2004-02-25 Created: 2004-02-25Bibliographically approved
4. Direct calculation of optical absorption amplitudes for trivalent rare-earth ions in LiYF4
Open this publication in new window or tab >>Direct calculation of optical absorption amplitudes for trivalent rare-earth ions in LiYF4
2002 In: Phys. Rev. B, ISSN 1098-0121, Vol. 65, p. 045111-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91420 (URN)
Available from: 2004-02-25 Created: 2004-02-25Bibliographically approved
5. Direct calculation of correlated absorption amplitudes for Nd:LiYF4
Open this publication in new window or tab >>Direct calculation of correlated absorption amplitudes for Nd:LiYF4
2003 In: Phys. Rev. B, ISSN 1098-0121, Vol. 68, p. 195105-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91421 (URN)
Available from: 2004-02-25 Created: 2004-02-25Bibliographically approved
6. Initial and final state effects in the x-ray absorption process of La1-xSrxMnO3
Open this publication in new window or tab >>Initial and final state effects in the x-ray absorption process of La1-xSrxMnO3
Show others...
2003 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 23, p. 235109-Article in journal (Refereed) Published
Abstract [en]

We have probed the electronic structure of La1-xSrxMnO3 using x-ray absorption spectroscopy, and compared our results to theory. It is shown that the O projected spectrum reveals a signal that is consistent only with hybridized and delocalized Mn d-states whereas the Mn projected spectrum reveals a signal that can only be reproduced by atomic like theory allowing for multiplet formation between the core hole and the valence electrons of the final state. Our results indicate that the ground state electronic structure has delocalized Mn d-states. This is discussed to be caused by a dynamical screening of the core hole created in the absorption process.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91422 (URN)10.1103/PhysRevB.68.235109 (DOI)
Available from: 2004-02-25 Created: 2004-02-25 Last updated: 2017-12-14Bibliographically approved
7. Origin of Magnetic Anisotropy of Gd Metal
Open this publication in new window or tab >>Origin of Magnetic Anisotropy of Gd Metal
Show others...
2003 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 91, no 15, p. 157201-157204Article in journal (Refereed) Published
Abstract [en]

Using first-principles theory, we have calculated the energy of Gd as a function of spin direction, θ, between the c and a axes and found good agreement with experiment for both the total magnetic anisotropy energy and its angular dependence. The calculated low temperature direction of the magnetic moment lies at an angle of 20° to the c axis. The calculated magnetic anisotropy energy of Gd metal is due to a unique mechanism involving a contribution of 7.5  μeV from the classical dipole-dipole interaction between spins plus a contribution of 16  μeV due to the spin-orbit interaction of the conduction electrons. The 4f spin polarizes the conduction electrons via exchange interaction, which transfers the magnetic anisotropy of the conduction electrons to the 4f spin.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91745 (URN)10.1103/PhysRevLett.91.157201 (DOI)
Available from: 2004-04-28 Created: 2004-04-28 Last updated: 2017-12-14Bibliographically approved
8. A program for accurate solutions of two-electron atoms
Open this publication in new window or tab >>A program for accurate solutions of two-electron atoms
2005 (English)In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 165, no 3, p. 260-270Article in journal (Refereed) Published
Abstract [en]

We present a comprehensible computer program capable of treating non-relativistic ground and excited states for a two-electron atom having infinite nuclear mass. An iterative approach based on the implicitly restarted Arnoldi method (IRAM) is employed. The Hamiltonian matrix is never explicitly computed. Instead the action of the Hamiltonian operator on discrete pair functions is implemented. The finite difference method is applied and subsequent extrapolations gives the continuous grid result. The program is written in C and is highly optimized. All computations are made in double precision. Despite this relatively low degree of floating point precision (48 digits are not uncommon), the accuracy in the results can reach about 10 significant figures. Both serial and parallel versions are provided. The parallel program is particularly suitable for shared memory machines such as the Sun Starcat series. The serial version is simple to compile and should run on any platform.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-91424 (URN)10.1016/j.cpc.2004.01.007 (DOI)
Available from: 2004-02-25 Created: 2004-02-25 Last updated: 2017-12-14Bibliographically approved

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