1,721,021 research outputs found
Luminescent properties of Pr3+ in titanates and vanadate: towards a criterion to predict 3P0 emission quenching
No full textExcited state dynamics of Pr3+ in YVO4 crystals
No full textThe quenching mechanism of the emission from the P-3(0) level of Pr3+ doped into YVO4 has been investigated by means of optical spectroscopy techniques. Continuous wave and time-resolved emission and excitation measurements have been carried out as a function of the temperature and of the dopant concentration in order to obtain information on the energy-transfer processes involved in the host sensitization of the red luminescence and in the depopulation of the emitting states. The experiments have also been extended to LaVO4:Pr3+ and YPO4:Pr3+, i.e., two crystals for which the P-3(0) emission is stronger than for YVO4:Pr3+, with the aim of studying the relationship between of the host properties and the optical behavior of the Pr3+ ion. (C) 2004 American Institute of Physics
Red luminescence induced by intervalence charge transfer in Pr3+-doped compounds
No full textThe excited state dynamics of the Pr3+ in oxide lattices is revisited in the light of the 'virtual recharge' model. The connection between the quenching of the blue-green emission from the P-3(0) level and the formation of a Pr3+ to metal intervalence charge-transfer state (IVCTS) is discussed on the basis of new experimental evidences. Updated information is presented, concerning the energy position of the lVCTS in various materials and its relation with the host properties. Finally, the limits of the proposed model are outlined and the perspectives for future work are pointed out
Luminescence of Pr3+ in titanates and vanadates : towards a criterion to predict 3P0 emission quenching
No full textExcited state dynamycs of Pr3+ in YVO4 crystals
No full textThe quenching mechanism of the emission from the 3P0 level of Pr3+ doped into YVO4 has been
investigated by means of optical spectroscopy techniques. Continuous wave and time-resolved
emission and excitation measurements have been carried out as a function of the temperature and of
the dopant concentration in order to obtain information on the energy-transfer processes involved in
the host sensitization of the red luminescence and in the depopulation of the emitting states. The
experiments have also been extended to LaVO4:Pr3+ and YPO4:Pr3+, i.e., two crystals for which the
3P0 emission is stronger than for YVO4:Pr3+, with the aim of studying the relationship between of
the host properties and the optical behavior of the Pr3+ ion
Luminescence properties of Pr3+ in titanates and vanadates: Towards a criterion to predict 3P0 emission quenching
No full textLuminescence spectra of Pr3+ in 15 titanate and vanadate lattices have been measured under LW excitation. They are characterized by a dominant red luminescence assigned to transitions from the D-1(2) level to the ground state. The quenching of the otherwise prominent blue luminescence from P-3(0) state is ascribed to a relaxation pathway involving a low-lying Pr3+-Mn+ (Mn+ = Ti4+ or V5+) intervalence charge transfer (IVCT) state. Complete quenching of the P-3(0) emission takes place when the IVCT bands are located in the 2650028 000 cm(-1) range and the shortest Pr3+-Mn+ distances are in the 3.15-3.30 angstrom rang
Quenching of lanthanide emission by intervalence charge transfer in crystals containing closed shell transition metal ions
No full textThe quenching of the luminescence originating from the excited states P-3(0) and D-1(2), of Pr3+ and D-5(3) and D-5(4) of Tb3+ has been studied in oxide crystals containing closed shell transition metal ions, such as titanates, vanadates, niobates, and tantalates. It has been shown that the emission from these excited states can be quenched by an intervalence charge transfer mechanism. The temperature dependence of the emission intensities has allowed estimating indicative activation energies for the crossover to the intervalence charge transfer state. In the case of Tb3+, the quenching gives rise to relatively short decay times for the D-5(4) state
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
