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| 2. |
- Edvardsson, Sverker, et al.
(författare)
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The use of CI calculated polarizabilities to study rare-earth CFP dependencies in the laser host RE:YLF
- 1999
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Ingår i: Materials Science Forum. - 0255-5476. ; 315/317, s. 407-414
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Tidskriftsartikel (refereegranskat)abstract
- It has earlier been shown that the Sternheimer method is appropriate in deriving crystal field parameters (CFP) for Pr3+ and Nd3+ doped in YLF or Nd3+ in YAG. In this connection, the dipole (αD) and quadrupole (αQ) polarizabilities for the whole rare-earth (RE) series will be presented. These are needed for the self consistent lattice summations performed. The various rare-earth wavefunctions needed for the computations are derived from the well known relativistic full Hartree-Fock code by R. D. Cowan. The main CFP behaviour for the various RE dopants in YLF are seen to agree fairly well with the experimentally fitted parameters. Covalency effects are, as expected, observed to be more important for higher order parameters. It is also seen that the contribution to the crystal field due to covalency is approximately constant for a given Btp. This observation is also supported by calculations of Newman. The shielding, nuclear antishielding factors and radial integrals for the whole RE series are also presented.
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| 3. |
- Edvardsson, Sverker, et al.
(författare)
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Use of polarized optical absorption to obtain structural information for Na1/Nd31 b9-alumina
- 1996
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Ingår i: Physical Review B, Condensed matter. - 0163-1829. ; 54:24, s. 17476-17 485
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Tidskriftsartikel (refereegranskat)abstract
- Part of the optical absorption spectrum is calculated for the Nd31-doped Na1 b9-alumina using a moleculardynamics-~MD! based approach. The Judd/Ofelt ~J/O! theory is modified ~and several approximations removed! to treat polarized transition intensities for rare-earth ions in a solid host. Stark-level energies and eigenfunctions of the ground state ~4I9/2! and excited multiplets (4F3/2,2P1/2) are also calculated for the local environments involved. Energies and polarized transition intensities between individual Stark levels are thus calculated simultaneously for several hundreds of MD-generated environments; summation gives the total bandshape. A high proportion of Beevers-Ross-site occupation ~.50%! is indicated for low Nd31 concentrations in b9-alumina. The contrary is observed experimentally for high Nd31 concentrations, i.e., then midoxygen site occupation dominates. It is demonstrated that ions in different local environments contribute differently to the absorption spectrum and, particularly, how the polarization of the various transitions changes for ions occupying different sites. Temperature dependence aspects are also considered
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| 4. |
- Klintenberg, Mattias, et al.
(författare)
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Calculation of energy levels and polarized oscillator strengths for Nd3+:YAG
- 1997
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Ingår i: Physical review. B, Condensed matter. - 0163-1829. ; 55:16, s. 10369-10375
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Tidskriftsartikel (refereegranskat)abstract
- The effect of an electrostatic crystal-field (CF) model on energy levels and oscillator strengths for Nd3+:YAG (where YAG denotes yttrium aluminum garnet) has been studied. Three parameters for the correction of the Slater integrals F2, F4, and F6 and one parameter to correct the spin-orbit constant for the effects of the linear configuration interaction have been introduced. The complete 364×364 energy matrix has been diagonalized directly. The various polarizabilities and shielding parameters used have been calculated by ab initio methods. All Stark levels within the Nd3+(4f3) configuration are presented. The calculated Stark splittings agree well with experiment. The electrostatic CF model used is therefore believed to be satisfactory. The eigenvectors of the complete energy matrix have been used to calculate oscillator strengths, which agree well with experiment. A refined Judd-Ofelt theory has been used. The Judd-Ofelt intensity parameters Ωλ are presented and found to be in excellent agreement with experiment. The temperature dependence of the spectrum is studied using a molecular-dynamics approach.
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| 7. |
- Klintenberg, Mattias, et al.
(författare)
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The use of molecular dynamics to simulate the temperature dependence of the calculated absorption spectrum for Nd3+:YAG
- 1999
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Ingår i: Materials Science Forum. - 0255-5476. ; 315-317, s. 42-50
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Tidskriftsartikel (refereegranskat)abstract
- The use of molecular dynamics (MD) and the inclusion of configuration interaction (CI) effects have been shown to be important in the simulation of polarized absorption spectra for rare-earth doped compounds. This work, focuses on how well the MD approach can account for the temperature dependence of the calculated absorption spectrum for Nd3+:YAG, using the standard MD pair-potential of the Born-Mayer-Huggins form. All simulated spectra are compared to the corresponding experimental spectra. The results indicate that the simple pair-potential must be replaced by a many-body potential to describe the motion of the ions with sufficient accuracy. They also suggest that an “effective temperature” (T') should be used in the MD simulation of the form T'=aT+b
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