Upconversion fluorescence spectroscopy of Er3+ pairs in CsCdBr3 a

Crystal growth, upconversion, and infrared emission properties of Er3+-doped KPb2Br5

“…Therefore, it appears unlikely that the emission lines observed above 1600 nm originate from isolated Er 3+ centers. The existence of different Er 3+ sites and possibly Er 3+ -pair centers in KPB, as observed for REdoped CsCdBr 3 [41,42], will be further explored in future investigations.…”

Upconversion and Anti-Stokes Processes with f and d Ions in Solids

“…As seen in the Introduction, upconversion by energy transfer is a generalization of Dexter's energy transfer 27 to the case where the activator is in a metastable state instead of being in its ground state; this requires the interaction between S and A ( H SA ) to be smaller than the vibronic interaction of S and A, so that both ions can be described by single-ion levels coupled to the lattice. It is generally the case since for fully concentrated rare-earth crystals or for clusters, pair level splitting is of the order of 0.5 cm -1 ; , in host with smaller concentrations, this interaction can be even weaker, whereas one-phonon or multiphonon sidebands may modulate the level positions by several hundreds of cm -1 . Further, upconversion requires the transfer probability for the second step ( W SA ) to be faster than radiative and nonradiative decay from the metastable level, that is W SA > τ -1 with τ measured intermediate state lifetime for ion A. W SA is obtained from where the wave functions are simple products of single-ion wave functions; ρ(E) describes the dissipative density of states due to the coupling with the lattice.…”

“…Such is the case when real single-ion levels do not exist to allow energy transfer; it is the case for Yb 3+ −Tb 3+ upconversion 55,66,67 or when the concentration is too small to allow efficient transfer by energy diffusion between sensitizers. Then cooperative upconversion is likely within clusters. , One may also look for crystal structures where the pair clustering is built-in. ,, …”

Tb3+ Luminescence in Tb-Doped and Tb/Gd-Doped CsCdBr3 Crystals: 5D4→5D3 Cross-Relaxation Rates in Tb3+ Pairs

“…The Ln 3+ environment is similar to that of the unsubstituted M 2+ ions, except that the Ln 3+ ions collapse slightly toward the vacancy, lowering the site symmetry to C 3 v . The Ln 3+ ions investigated optically in one or more of the CsMX 3 hosts include singly doped Pr 3+ , − Nd 3+ , − Tb 3+ , , Ho 3+ , , Eu 3+ , , Er 3+ , − Tm 3+ , and Ce 3+ 26 systems, and codoped Tm 3+ −Pr 3+ , Tm 3+ −Ho 3+ , Yb 3+ −Er 3+ , Gd 3+ −Er 3+ 30 and Ce 3+ −Tm 3+ 31 systems. By far, the majority of these spectroscopic investigations of lanthanide pairs in these hosts have centered on upconversion processes, especially in Er 3+ :CsCdBr 3 , wherein pair luminescence can be obtained at wavelengths shorter than the excitation wavelength(s).…”