No abstract

Infrared and Raman spectra are presented for the magnesium dihalides isolated in matrices. Of particular interest is the Ramen observation of the ν1 symmetric stretch in argon matrices at 550.0, 326.5, 197.9, and 147.6 cm−1 for MgF2, MgCl2, MgBr2, and MgI2, respectively. For MgF2, ν1 had previously been assigned to a strong infrared feature near 480 cm−1, and this activity (along with isotopic frequency shifts) has been cited as evidence for a nonlinear structure for MgF2. The present results undermine this argument and a linear structure is favored, a result consistent with the failure to detect a dipole moment in gas phase electric deflection measurements. Force constants calculated for a linear structure are compared with values obtained from several theoretical models and the results favor an ion–ion interaction model in which the bonding is essentially ionic. Finally, features due to MgX2 dimers are assigned on the basis of a bridged D2h model, and some features attributed to weak complexes between MgX2 and impurities in the matrix are discussed.

The influence of self-absorption in a 4-dicyano-methylene-2-methyl-6-p-dimethyl amino-styrl-4H-pyran (DCM) doped polymethylmethacrylate (PMMA) optical waveguide on the light transport efficiency has been evaluated. A Monte Carlo technique was used to simulate intermolecular energy transfer and calculate the energy emission profile of an active waveguide. The calculated and measured edge emission profiles were found to be in excellent agreement. The edge emission spectra for various distances of excitation from the edge were used to estimate the DCM self-absorption cross section.

The performance of organic dyes in PMMA has been evaluated in a three-layer planar luminescent solar concentrator. The single plate and combined three-plate efficiencies have been measured for a number of dyes, and results of one typical combination are reported here. A detailed characterization of the spectroscopic properties of the dye molecules as well as the device dependent and device independent parameters of the plates allow comparison between measured and predicted efficiency. Our results demonstrate the presence of a significant positive synergism for the multilayer device.