The Absorption Spectra of Manganese Fluoride, Zinc Fluoride, and Manganese-Activated Zinc Fluoride

Thin films of MnF2, ZnF2, and ZnF2:Mn have been prepared by evaporation, and their optical absorption spectra have been measured from 1500 to 2600A. The absorption coefficient of MnF2 has a maximum of 8.64×104 cm−1 at 1613A, corresponding to an oscillator strength of 0.042; while there appears to be a maximum of lower value at 1470A for ZnF2. An unresolved weaker band at 2050A is also evident for MnF2. For the phosphor, ZnF2:Mn, the absorption coefficient is intermediate between those of ZnF2 and MnF2, but the peak characteristic of the Mn++ activator is shifted to 1666A and the oscillator strength of the transition is increased to 1.2. The relative excitation spectrum of ZnF2:Mn was determined, and maximum response occurred between 1600 and 1670A, indicating that radiation in the strong absorption band characteristic of the activator is most effective in exciting luminescence. Less efficient excitation occurs to 2200A. It is concluded that a transition to an excited atomic state of the activator, rather than an electron transfer process, is responsible for the first absorption peaks in MnF2 and ZnF2:Mn.