Raman spectra of hydroxide-halide melts

The Raman spectra of molten binary mixtures based on sodium hydroxide and containing (mol %) 35 NaCl, 30 NaBr, and 30 NaI have been recorded at various temperatures. An increase in the vibrational frequency and the force constant of the O-H bond is detected under isothermal conditions upon a variation of the anionic composition of a melt in the series I ?? Br ?? Cl. Based on the experimental data, the viscosity of the hydroxide-halide melts is estimated.     

Raman spectroscopy of glasses and melts of the Na<Subscript>2</Subscript>O-GeO<Subscript>2</Subscript> system

Glasses and melts of the system X mol % Na₂O · GeO₂ (X = 0, 10, 20, 30) are investigated using high-temperature Raman spectroscopy. Addition of an oxide modifier is shown to bring about an increase in the coordination number of central germanium atoms along with the depolarization of the three-dimensional GeO₂ network. The glass-melt transition in germanate systems with a low oxide-modifier content is accompanied by the transition of six-coordinated germanium atoms into four-coordinated (with oxygen) ones and a simultaneous formation of nonbridge oxygen atoms.     

Raman spectroscopy of the structures of Li2O-SiO2 and Li2O-GeO2 melts

An analysis of the Li₂O-SiO₂ and Li₂O-GeO₂ systems in the temperature range from 298 to 1373 K has been performed by Raman spectroscopy. A comparison of the spectroscopic data for the crystalline phases, glasses, and melts allowed us to determine the main anion groups existing in these systems and to establish the structural changes induced by changes in the temperature and composition.     

Raman difference spectroscopy of tertiary and quaternary structure changes in methaemoglobins

There have been several resonance Raman scattering investigations of the effect of inositol hexaphosphate (IHP) on methaemoglobins. In those studies the sensitivity for detecting frequency differences was limited to 1-2 cm-1, and consequently frequency differences were not detected although spectral intensity differences due to changes in spin equilibria were. Shelnutt et al. recently reported on the observation of frequency differences induced by changes in the quaternary structure of chemically modified deoxyhaemoglobins. An improved Raman difference spectroscopic technique with 0.1 cm-1 sensitivity allowed the detection of these differences. We report here the application of this technique to a series of methaemoglobins with and without the addition of IHP. In addition to the intensity changes resulting from changes in the spin equilibria, we have observed frequency differences. In all liganded methaemo-globins that we examined a decrease in frequency of the mode in the 1,370 cm-1 region was observed on addition of IHP. In those in which a quaternary structure change is known to occur the frequency difference is greater than 0.5 cm-1. In those in which no quaternary structure change occurs [metHbA(CN-) and methHbA(N-3)] the frequency difference is smaller (approximately 0.15 cm-1).