N-lines and chromium-pairs in the luminescence spectra of the spinels ZnAl2O4:Cr3+ and MgAl2O4:Cr3+ |
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Authors: | J. Derkosch W. Mikenda A. Preisinger |
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Affiliation: | Organisch-Chemisches Institut, Universität Wien, Austria;Institut für Mineralogie und Kristallographie, Universität Wien, Austria |
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Abstract: | It is shown that the N-lines in the luminescence spectra of the two spinels ZnAl2O4:Cr3+ and MgAl2O4:Cr3+ exhibit quite similar dependencies on chromium concentration, excitation frequency, and thermal treatment of the samples. While most of these lines are structure dependent, the line N4 at and two very weak lines are in both cases due to chromium-pairs. The exchange Hamiltonian Hex = JS1 · S2 + j(S1 · S2)2 used for the ground-state splitting is fitted by the parameters J = 40.9 cm?1, j = 1.5 cm?1 and J = 45.6 cm?1, j = 2.0 cm?1 for ZnAl-spinel and MgAl-spinel, respectively. The differences between the spectra of low-doped and high-doped samples are in both cases caused by the existence of a phonon sideband of the N4-line, which is in many respects similar to the well-known phonon side band of the R-line. |
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Keywords: | Correspondence should be addressed to: J. Derkosch Org. Chen. Inst. d. Universität Währinger Straße 38 A-1090 Vienna. |
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