Energy migration within the 2E state of Cr3+

Abstract

Please cite this article in press as: M. a b s t r a c tExcitation energy migration is an important phenomenon at high concentration of luminescent chromophores. In crystalline solids it results in a quenching of the intrinsic luminescence of the chromophore as the excitation energy migrates to impurity centres or other forms of trap sites. As concluded from the extensively studied systems where Cr 3+ is doped as the active chromophore into inert host lattices, energy migration in crystalline solids is usually a phonon-assisted process, in which the simultaneous creation or annihilation of phonons helps to bridge the energy miss-match in the energy levels of two neighbouring chromophores within a inhomogeneously broadened absorption band. However, in the three-dimensional network systems [Ru(bpy) 3+ . In addition to the common temperature dependant phonon-assisted process, a resonant process between the zero-field split components of the 4 A 2 ground state leading to a multi-line pattern in a fluorescence line narrowing spectrum and a quasi-resonant process within the same component leading to fast spectral diffusion can be identified at very low temperature. The parameters governing these processes are discussed and the behaviour of the model systems is compared to more conventional doped oxides and related systems.

Synthesis and Optical Properties of Al2O3:Cr3+ Powders

“…This result shows that the lines at 659, 699, 674, 678, 700, 706, 712, and 725 nm are phonon-sidebands of the lines R 1 and R 2 . The PLE spectra consist of two strong broad absorption bands with peak positions at around 399 and 556 nm, corresponding to spin-allowed [5,6]. Beside, a weak sharp peak at 692 nm corresponding to the transitions from the basic level 4 A 2 ( 4 F) to the lowest excited level 2 E( 2 G), is also observed.…”

“…6 [4][5][6]. Figure 10 shows the PLE spectra of the Al 2−x Cr x O 3 samples with x = 0.005, heat-treated at 1300…”

Physical Chemistry at the University of Geneva

“…11). In addition to the well-known phonon-assisted process at elevated temperatures, two types of resonant and thus energy selective processes lead to a multi-line pattern and fast spectral diffusion, respectively, at 1.4 K. [28,29] In the complex [Ru(bpy) 2 dppz-TTF] 2+ (Fig. 12) irradiation into the metal-ligand charge transfer (MLCT) bands results in both luminescence as well as the creation of a comparatively long-lived charge separated state (τ = 2.4 µs).…”

A model for spectral diffusion induced by resonant energy migration applied to the 4A2→2E transition of Cr3+ in [Cr(ox)3]3− (ox=C2O42−)

“…This leads to the sequential appearance of additional sharp lines spaced by the ground-state ZFS in the FLN spectrum across the inhomogeneous line [10]. The second one is a quasi-resonant process between spectral neighbours and manifests itself by rapid spectral diffusion [9]. The third one is the well-known phonon-assisted process setting in at higher temperature.…”

“…In fact, they allow a clear distinction between different mechanisms for energy migration as depicted in Fig. 1 [9]. Fluorescence line narrowing (FLN) spectroscopy showed that at cryogenic temperatures, where phonon-assisted energy migration is negligible, two different types of resonant energy migration may take place.…”