Electronic structure of luminescence center of ZnS:Ag phosphors

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Abstract
The fluorescence, excitation, and reflection spectra of ZnS:Ag phosphors at room temperature and at 77°K were measured in detail. A number of excitation bands characteristic of Ag+ center were found in the spectral region from about 3400 to 5000 Å. The ligand‐field analysis of the excitation spectra was performed, based on the localized center model of luminiscence. Good agreement between the calculated and experimental energies was obtained. Thus the excitation and absorption spectra of ZnS:Ag phosphors are unambiguously correlated to the electron transitions between the ground state A1(1S0) with 4d10 configuration and the excited states T2(1D2, 3D2 and 3D3) in zincblende, and A1 and E (1D2, 3D1, 3D2 and 3D3) in wurtzite, having 4d95s configuration. The well‐resolved blue, bluish green, and green emission bands characteristic of Ag+ center were observed and ascribed to the reverse process of the absorption transitions. Furthermore, the excitation lines and bands in the uv region below about 3400 Å were analyzed in terms of excitons or phonon‐coupled excitons.