Spectroscopic studies in highly symmetrical crystals
Description
The highly symmetrical crystals referred to on the title page are of the A$\sb{\rm n}$MX$\sb{\rm n + 2}$ class, where A is a univalent cation, M is a divalent metal, and X is a halide. In addition to being highly symmetrical, many of these crystals exhibit specific dimensionality with respect to the ordering of their internal bulk metal ions The structures of these lattices can be described in terms of how their MX$\sb6\sp{4-}$ moities join to each other. The MnX$\sb6\sp{4-}$ moities join at faces in CsMnBr$\sb3$, at faces and corners in RbMnCl$\sb3$, and only at corners in Rb$\sb2$MnCl$\sb4$. Thus, CsMnBr$\sb3$ is composed of quasi one dimensional chains with the Cs$\sp{+}$ ions providing charge compensation between the chains$\sp2$. The RbMnCl$\sb3$ is a quasi three dimensional system with two distinct sites for the manganeses$\sp{3}$. The Rb$\sb2$MnCl$\sb4$ forms quasi infinite sheets isostructural with the K$\sb2$NiF$\sb4$ lattice$\sp3$ The presence of an emission feature at $\sim$650 nm. in crystals of RbMnCl$\sb3$, Rb$\sb2$MnCl$\sb4$, and CsMnBr$\sb3$ doped with chromium (II) has stimulated our interest in that spectral feature. Work has been completed in our laboratories characterizing the chromium (II) luminescences$\sp4$. The chromium (II) visible luminescence is attributed to relaxation from the $\sp3$E to $\sp5$E state and the infrared luminescence is due to relaxation from the $\sp3$E to $\sp3$T state Sprectra of CsMgCl$\sb3$ and CsCdBr$\sb3$ doped with Mo$\sp{3+}$ and Mo$\sp{3+}$ along with Li$\sp{+}$ show sharp emission features between 700 nm. and 740 nm., which is of the correct wavelength for the radiation resulting from relaxation from the $\sp2$T$\sb2$ excited state reported by Flint et al$\sp5$. Excited state lifetimes of the Mo$\sp{3+}$ centers have been measured in our laboratories The luminescence dynamics of the bulk manganese has been investigated in CsMnBr$\sb3$ doped with trapping centers (Er$\sp{3+}$, Fe$\sp{2+}$ and Cr$\sp{2+}$) and scattering centers (Mg$\sp{2+}$) The electron paramagnetic resonance (EPR) spectra has been recorded for octahedral manganese (II) doped in selected A$\sb{\rm n}$CdCl$\sb{\rm n + 2}$ lattices. It has been found that the crystal structure of the solution grown RbCdCl$\sb3$ is different from its melt grown analog$\sp8$. (Abstract shortened with permission of author.)