Effect of M+2 ions on the luminescence of Pb+2 in NaCl

The effect of additional doping with M⁺² ions on the luminescence of NaCl:Pb⁺² has been systematically investigated. The data show that the same two emissions at 310 and 380 nm are observed for mixed Pb⁺²-M⁺² clusters as for Pb⁺² aggregates. Moreover, the presence of a M⁺² ion associated to a Pb⁺² ion in a mixed cluster shifts the 310 nm emission (predominantly observed for free Pb⁺²-vacancy dipoles) to 380 nm. The results are consistent with the Fukuda's model, involving an emission at 310 nm from tetragonal (T) minima in the adiabatic potential energy surface (APES) and another one from less symmetry (X) minima at 380 nm. The data for NaCl:Pb⁺²:Mn⁺², show that an excitation transfer is taking place from the X minima of the ³T_1u state of Pb⁺² to Mn⁺².