Abstract: | The optical absorption bands of aqueous 0·05 M Sn2+ in 7 M LiI at 77°K appear at 361, 352, 325, 310, 300, 292 and 262 nm. They are considered to be the A1, A2, B, C1, C2, C3 and D′ bands since the positions and relative intensities lie within the range of those bands for Sn2+-doped alkali iodide crystals. Upon warming the glass there is an uncorrelated increase in the B band and a decrease in the A1 band. In 3·6, 4·1, 4·6 and 5·1 M CaCl2 glasses with 5×10?3 M Sn2+ the A1 and A2 bands show uncorrelated increases with increasing concentration of Cl?. Comparable observations are reported for Pb2+-doped glasses of lithium halides and CaI2. In general the spectra of the Sn2+- and Pb2+-doped glasses correlate well with those of the corresponding crystal systems. The effect of temperature and halide-ion concentration are attributed to shifts in chemical equilibria among the well-known halo complexes, MXn2?n MXn?11?n+X?, each having a characteristic, absorption and emission. Absorptions may be attributed to M2+(3P1 ← 1S0) and M2+(1P1 ← 1S0) in the complex, shifted by partially covalent bonding of n halide ions. |