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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependence of the lifetime of Cr3+ luminescence in garnet crystals I (1990)
    Springer
    Applied physics 50 (1990), S. 425-431 
    Details
    ISSN: 1432-0649
    Keywords: 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The lifetimes of the R-lines from the 2 E level and the broad bands from the 4 T 2 level of Cr3+ ions in various garnet crystals vary with the energy separation between the 2 E and 4 T 2 levels, which change systematically with the composition of host crystal. The trend of the Cr3+ lifetimes, as well as their temperature dependences in garnet crystals, is explained by zero-point vibration and phonon-assisted tunnelling between the 2 E and 4 T 2 states of Cr3+ ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325096
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  • 2
    Electronic Resource
    Electronic Resource
    Polarization of emission spectra from Ti3+-doped oxide crystals (1991)
    Springer
    Applied physics 52 (1991), S. 225-229 
    Details
    ISSN: 1432-0649
    Keywords: 42.55R ; 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ti3+ ion in YAlO3 (YAP), Y3Al5O12 (YAG), and Al2O3 crystals occupies distorted octahedral sites relative to the nearest neighbour ligand ions. Such distortions are of even-parity in YAG where the zero-phonon lines in emission occur via magnetic dipole transitions. In contrast, the zero-phonon transitions occur by electric dipole processes in Ti3+:YAP and Ti3+:Al2O3 where there are odd-parity distortions from octahedral symmetry. This paper reports measurements of the zero-phonon lines of Ti3+ ions in YAP, YAG, and Al2O3 at 10 K. The zero-phonon lines of Ti3+:YAP are strongly polarized perpendicular to the tetragonal axis and those of Ti3+:Al2O3 parallel to the trigonal axis. The experimental results are shown to be in accord with a molecular orbital model of the radiative transition according to which the transition intensities derive from odd-parity ligand wavefunctions induced into even-parity ground and excited Ti3+ wavefunctions by odd-parity crystal distortions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750955
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  • 3
    Electronic Resource
    Electronic Resource
    Optical spectroscopy of Cr3+ ions in LiF single crystals (1991)
    Springer
    Applied physics 53 (1991), S. 209-213 
    Details
    ISSN: 1432-0630
    Keywords: 42.70 ; 78.50 ; 78.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper reports on the luminescence spectrum, its excitation-wavelength dependence and decaytime of Cr3+:LiF crystals. In contrast to Al2O3 and MgO, where the Cr3+ luminescence at low temperature is due to the R-line and its vibronic sideband, luminescence from Cr3+:LiF is assigned to the broad-band 4 T 2→4 A 2 transition. A periodic structure in the vibronic sidebands of this transition occurs with energy separations of ca. 60 meV. The linear polarisation of the vibronic sidebands shows that their radiative transition takes place from the lowest excited level of the 4 T 2 state, i.e. 4 B 1, into the 4 A 2 ground state of Cr3+ ions in orthorhombic symmetry sites. The crystal-field parameters calculated from the experimental data, and luminescence decay-time of the two polarized configurations of the 4 B 1(4 T 2)→4 A 2 transition are also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324253
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  • 4
    Electronic Resource
    Electronic Resource
    Luminescence from Ti2+ ions in LiF crystals (1991)
    Springer
    Applied physics 53 (1991), S. 214-217 
    Details
    ISSN: 1432-0630
    Keywords: 42.70 ; 78.50 ; 78.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Luminescence of Ti2+: LiF crystals in the wavelength range 650–900 nm excited using laser radiation is reported. The values of 10Dq and the Racah B parameter obtained from the present results indicate that in LiF the 1 E, 1 T 2, and 3 T 2 energy levels are almost at the “cross-over” point in the Tanabe-Sugano diagram. In consequence photoluminescence from all three energy levels to the ground state is observed. At low temperature (T ∼ 14 K) the emission is mainly due to sharp emission lines with weak vibronic structure due to the 1 E, 1 T 2→3 T 1 transitions of Ti2+ ions. The 3 T 2→3 T 1 broad-band emission is weak at low temperature, becoming stronger at 300 K due to a phonon-assisted tunnelling process, similar to that observed in Cr3+: garnets [1]. The excitation spectrum of these lines is a broad peak at 590 nm due to absorption in the 3 T 1→3 T 2 transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324254
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  • 5
    Electronic Resource
    Electronic Resource
    Radiative and non-radiative decays from the excited state of Ti3+ ions in oxide crystals (1990)
    Springer
    Applied physics 51 (1990), S. 329-335 
    Details
    ISSN: 1432-0649
    Keywords: 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fluorescence spectra of Ti3+ in Y3Al5O12 (YAG), Al2O3 (sapphire), YAlO3 (YAP) observed at 10 K are composed of zero-phonon lines accompanied by the broad vibronic sidebands. The temperature dependence of the fluorescence lifetime and of the total intensity of the broadband measured in YAG and Al2O3 indicate that the radiative decay times from the excited states are nearly constant in the range 10–300 K. This demonstrates that the broadband radiative emissions in Ti3+:YAG and Ti3+:Al2O3 are due to magnetic dipole transitions or to electric dipole transitions induced by static odd-parity distortion, respectively. The decrease of the fluorescence lifetime with increasing temperature in Ti3+:YAG and Ti3+:Al2O3 is due to non-radiative decay from the excited state which occurs through phonon-assisted tunnelling between the excited and ground states. The radiative decay of Ti3+:YAP is enhanced with increasing temperature, indicating that radiative decay rate contains a term associated with odd-parity phonons. Nevertheless, a non-radiative decay rate of 3.6 × 104 s−1 observed in the temperature range 10–300 K is due to excited state absorption, which depopulates the excited state and quenches the fluorescence at the laser wavelength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348969
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  • 6
    Electronic Resource
    Electronic Resource
    Polarization of emission spectra from Ti3+-Doped oxide crystals (1991)
    Springer
    Applied physics 52 (1991), S. 122-131 
    Details
    ISSN: 1432-0649
    Keywords: 42.55R ; 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The photoluminescence spectra of Ti3+-doped YAlO3, Y3Al5O12 and Al2O3 crystals display weak zero-phonon lines and broad vibronic side bands. The zero-phonon lines are due to the splitting of the 2 T 2g ground state into three Kramers' doublets by the combined effects of static axial crystal field, Jahn-Teller effect and spin-orbit interaction. A molecular orbital method is used to calculate the relative intensities and polarizations of both zero-phonon lines and broad band in terms of the mixing of odd-parity ligand wavefunctions into even-parity Ti3+ wavefunctions by odd-parity crystal fields of T 1u and T 2u symmetries at sites with tetragonal and trigonal symmetries. The odd-parity distortions may be static or dynamic and are of crucial relevance in determining the strength of vibronically induced transitions. In general, selection rules for optical spectra are uniquely determined by group theory. The relevance of the molecular orbit description of the d-d transitions is that it permits a physical interpretation of the strength of optical spectra in terms of the covalent charge transfer from ligand ions to central ions induced by odd-parity crystal field distortion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357666
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature dependence of the lifetime of Cr3+ luminescence in garnet crystals (1990)
    Springer
    Applied physics 51 (1990), S. 132-136 
    Details
    ISSN: 1432-0649
    Keywords: 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The coexistence of sharp R-lines from the 2 E state and the broad band from the 4 T 2 state in the photoluminescence spectra of Cr3+:Gd3Sc2Ga3O12 (GSGG) and Cr3+:Y3Ga5O12 (YGG) is observed at low temperature (10K). The decay lifetimes of the broad emission bands of Cr3+ in GSGG and YGG are very close to those of the R-lines being, respectively, 0.23 ms and 2.5 ms. These results are explained in terms of the extent of the mixing of the 4 T 2 vibronic wavefunction with that of the 2 E lowest excited state by tunnelling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326013
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