Sara García-Revilla, Pascal Gerner, Oliver S. Wenger, Hans U. Güdel and Rafael Valiente
Visible Ni²⁺ upconversion luminescence in Ni²⁺, Yb³⁺ co-doped CsCdBr₃
Chem. Phys. Lett. 401, 492-496 (2005)                 

Abstract: Excitation around 10200 and 10600 cm^–1 into the absorption peaks of Yb³⁺ leads to visible Ni^{2+ 1}T_2g ³A_2g upconversion luminescence in the doubly doped CsCdBr₃: Ni²⁺, Yb³⁺ at cryogenic temperatures. The excitation spectrum indicates that an Yb³⁺ absorption step is involved in the upconversion process leading to visible Ni²⁺ luminescence. This process via Yb³⁺ excitation is more efficient than the upconversion mechanism involving only Ni²⁺, which is observed in the title compound for excitation energies above 11200 cm^–1. Upconversion lifetimes point towards an energy transfer upconversion mechanism for the Ni²⁺/Yb³⁺ system in CsCdBr₃.