Energy transfer from Pb²⁺ to Mn²⁺ in fluorescent halite from Salton Sea, California

Abstract

Photoluminescence (PL) properties of halite from Salton Sea, California, USA, are investigated at 10, 80, and 295 K. The color of clear part of this halite is transparent under daylight, and the fluorescence under UV light at 253.7 nm is orange-red. The orange-red emission band at 640 nm is assigned to the electronic transitions within the 3d⁵ configuration of Mn²⁺ in halite (NaCl). The excitation spectrum of the orange-red fluorescence consists of unefficient excitation bands due to Mn²⁺ and efficient excitation bands due to Pb²⁺. The existence of the Pb²⁺ bands in the excitation spectrum of the Mn²⁺ fluorescence suggests that there is an excitation process due to the energy transfer with the resonance type from Pb²⁺ to Mn²⁺. Thermal quenching of the specimen is undertaken, and it is clarified that the clusters of the Pb²⁺-vacancy pairs play an important part in the orange-red fluorescence from the halite. Analysis by inductively coupled plasma-mass spectrometry (ICP-MS) reveals that this halite includes Mn (98 μg/g) and Pb (640 μg/g).