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One-dimensional energy transfer in GdCl3

1988; American Institute of Physics; Volume: 89; Issue: 9 Linguagem: Inglês

10.1063/1.455544

1520-9032

Rachid Mahiou, B. Jacquier, C. Madej,

Photochemistry and Electron Transfer Studies

We report the observation of the intrinsic fluorescence of anydrous gadolinium trichloride GdCl3 when laser light is absorbed into the first excited state 6P7/2. With the aid of a frequency doubled pulsed dye laser, we are able to analyze carefully the excitation and emission spectra as well as the decay times over a range of temperatures including that at which the material undergoes a ferromagnetic transition at 2.2 K. At 4.4 K and above, experiments at low excitation density (N0<1014 excited ions/cm3) show that the intrinsic and the impurity induced trap fluorescence dynamics are well described in terms of a fast diffusion and trapping model. When the excitation density is increased anti-Stokes fluorescences appear efficiently; they are assigned to the 6D9/2, 6I7/2→8S7/2 transitions. High excitation density effect on the intrinsic decay as well as the decay of the anti-Stokes fluorescence are nicely reproduced by a theoretical model involving mainly an exciton–exciton annihilation process. Moreover, an excited state absorption mechanism contributes notably to the anti-Stokes fluorescence intensity at t=0 with increasing the excitation density. In the ferromagnetic phase of GdCl3, at 1.5 K, the one-dimensional nature of the exciton diffusion (8S7/2↔6P7/2) is confirmed by the ‘‘incoherent’’ exciton decay analysis using an appropriate model recently developed by Cibert et al. Finally a diffusion length spreading over 2500 visited Gd3+ normal sites is evaluated, knowing the hopping time as a function of the nearest neighbor interactions (nn) in the crude approximation of an ideal two level system in a linear chain of atoms.