Raman spectroscopy, ambient-temperature

Murphy, P. J., LaGrange, M. S. (1998). Raman spectroscopy of gold chloro-hydroxy speciation in fluids at ambient temperature and pressure a re-evaluation of the effects of pH and chloride concentration Geochimica et Cosmochimica Acta, 62(21-22), 3515-3526. doi 10.1016/S0016-7037(98)00246-4... 

Durig and Little (1981) determined the conformational barriers to internal rotation of methyl vinyl ketone by IR and Raman spectroscopy. They recorded IR spectra of the gaseous and the solid states and the Raman spectrum of the liquid state. They also determined the potential function for internal rotation of the asymmetric top and obtained the following potential constants VI = 180 9, V2 = 827 107, V 3 = 113 8, and V4 = 150 34 cm. According to these data, the s-trans conformer is the predominant form at ambient temperature, and the enthalpy difference between the s-trans and the s-cis conformer in the gas phase is 280 cm. The relative intensities of the Raman bands as a function of the temperature afford an enthalpy difference of 172 cm for the liquid. 

Raman spectroscopy provides a rapid and convenient tool for structure analysis without having to use diffraction techniques. Subsequently. Raman spectroscopy was used to study the structures, phase equilibria, and kinetics of gas hydrates at high pressure and close to ambient temperatures. By monitoring the Raman spectra of guest molecules, the phase transition from Stmcture I to II hydrate for an ethane-methane gas mixture was identified for the first time. This was an xmexpected result, because both methane and ethane form Structure I hydrate. ... 

Long ago Bernal and Fowler (1933) introduced the concept of the structural temperature of aqueous solutions. This is that temperature, Tsu, at which pure water would have effectively the same inner structure as the water in a solution at the temperature T. They suggested that Tstr could be estimated from viscosity, x-ray diffraction, Raman spectroscopy, etc., but did not provide explicit methods and values. TheD20 vs. H2O isotope effects on x-ray Raman spectra indicate (Bergmann et al. 2007) that D2O has a structural temperature lower by 20 K than H2O at ambient conditions. This is ascribed to the inherently stronger hydrogen bonding in the heavy water. The concept of structural temperature has by now been practically abandoned, however. 

The interaction between zinc oxide and stearic acid in a medium suitable to simulate a vulcanized system has been investigated [65] experimentally using vibrational spectroscopic technique. Confocal Raman micro spectroscopy revealed that at ambient temperature both components are phase-separated in the form of microcrystals. When the reaction temperature (SO C and above) is reached only zinc oxide is present in the form of particles while the stearic acid melts and gets molecularly dispersed within the rahher matrix. The analysis points to a core-shell structure of the reacting system stearic acid diffuses to the surface of zinc oxide domains causing the shrinkage of the zinc oxide core and the formation of a shell of increasing thickness made of zinc stearate. 

Other work using picosecond laser spectroscopy has shown that these reactions proceed via a solvent intermediate, M(CO)5(solvent), which forms in a few picoseconds after the laser pulse and then decays to products. Lee and Harris have observed formation of the solvated species Cr(CO)5(C5H,2) with t = 17 ps and the decay of the vibrationally excited Cr(CO)j with t 21 ps (apparently at ambient temperature). These observations are at variance with those of Spears and co-woikers, who claim that the bare Cr(CO)j persists on the 100-ps time scale at 22°C. Hopkins and co-workers have used resonance Raman detection to show that the 100-ps process is due to thermal relaxation of the excited vibrational state, probably of Cr(CO)5(CgH,2). 

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