Crystal-field analysis for REp>3+p> ions in laser materials: I. Absorption spectra and energy levels calculations for Ndp>3+p> and Prp>3+p> ions in ABCO₄ crystals

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• 作者：M. Karbowiakp>ap>p> ; p>p>karb@wchuwr.pl"" rel=""nofollowp> ; C. Rudowiczp>bp>
• 关键词：Optical spectroscopy ; Crystal (ligand) field parameters ; Tetragonal and triclinic site symmetry ; Prp>3+p> and Ndp>3+p> ions ; SrLaAlO₄ ; Ndp>3+p> ; SrLaGaO₄ ; Ndp>3+p> ; CaNdAlO₄ ; SrLaAlO₄ ; P
• 刊名：Chemical Physics
• 出版年：2011
• 出版时间：26 May 2011
• 年：2011
• 卷：383
• 期：1-3
• 页码：68-82
• 全文大小：1255 K

文摘

Low temperature polarized absorption spectra are analyzed to achieve assignments of energy levels for Ndp>3+p> ions at tetragonal C_4v symmetry sites in SrLaAlO₄:Ndp>3+p>, SrLaGaO₄:Ndp>3+p>, and CaNdAlO₄ as well as Prp>3+p> ions at C_4v sites in SrLaAlO₄:Prp>3+p> crystals. The C_4v selection rules for polarized electric dipole transitions are strictly obeyed for Prp>3+p> ion doped into SrLaAlO₄. However, for Ndp>3+p> ions in the same crystal neither the C_4v polarization rules nor the C₄ ones are strictly confirmed. This is explained in terms of structural disorder. The experimental energy levels for Prp>3+p> and Ndp>3+p> ions in these crystals were analyzed in terms of the free-ion parameters and the crystal field (CF) ones, B_kq, assuming C_4v site symmetry and using the starting values of B_kq’s obtained from superposition model (SPM) analysis. A good agreement between the calculated and experimental energy levels was obtained with rms deviations in the range from 20.5 to 23.6 cmp>−1p> for Ndp>3+p>-doped crystals and 19.8 cmp>−1p> for SrLaAlO₄:Prp>3+p>. Using the CF parameters B_kq optimized in fittings of the calculated and experimental energy levels, the model parameters, i.e. the intrinsic parameters and the power law exponents t_k, were determined and compared with those for other similar systems hitherto studied. The obtained values of the intrinsic parameters may serve as a starting point for SPM analysis of CF parameters for other systems, particularly those exhibiting low symmetry of metal centers. As an example of such systems, we consider Ndp>3+p> ions at triclinic C₁ symmetry sites in BaLaAlO₄:Ndp>3+p> crystals. Low temperature polarized absorption spectra for this system is also analyzed yielding assignments of energy levels. The results of preliminary low symmetry CF analysis carried out for BaLaAlO₄:Ndp>3+p> are presented.