Electronic Structure of Luminescence Centers of ZnS Phosphors Activated with Impurity Ions of s2 Configuration. II. ZnS:Pb (Zinc-Blende) Phosphors

Abstract

$\mathrm{A,\; B}$ , and $C$ bands with peaks at about 4910, 4220, and 3990 Å (mean values for split subbands at 77°K), respectively, were found in the excitation or reflection spectra of visible region of ZnS:Pb (zinc‐blende) phosphors. These bands were analyzed by means of Sugano's molecular‐orbital theory and identified unambiguously as those due to the resonance transitions from the ground state ${\mathrm{(A}}_1{,}^1{S}_0)$ to the excited states ${\mathrm{(T}}_2{,}^3{P}_1{\mathrm{;\; T}}_1$ and ${\mathrm{E,}}^3{P}_2$ ; and $T_2{,}^1{P}_1$ , respectively) in the localized Pb²⁺ center at lattice site. The observed orange (6400 Å), green (5000 Å), and yellow (5850 Å) emission bands were also unambiguously correlated to the inverse transitions to the $\mathrm{A,\; B}$ , and $C$ absorption transitions, respectively. The assignment for the excitation bands or lines in the uv region were performed satisfactorily. The observed singlet, doublet, and triplet structure of $\mathrm{C,\; B}$ , and $A$ excitation bands, respectively, or the triplet structure of the green emission band were interpreted in detail in terms of dynamic JT effect, leading to satisfactory understanding of the preparation conditions for the green‐ and orange‐emitting phosphors.