Vibrational spectra of hydrated rare earth orthophosphates

Weinschenkite-type LnPO₄·2H₂O (Ln is Gd, Tb, Dy, Ho, Y, Er, Tm or Yb) and rhabdophane-type, LnPO₄·H₂O (Ln is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb or Dy) have been investigated by IR absorption spectroscopy (4000–400 cm⁻¹) and Raman scanning spectroscopy (1400–100 cm⁻¹).The IR spectra of weinschenkite-type LnPO₄·2H₂O (Ln is Gd→Yb) are characterized by a band at 750±6 cm⁻¹ and the occurrence of a doublet in the region of the HOH bending vibrations, the low-frequency component exceeding the first high-frequency component in intensity. This rather peculiar pattern has already been observed in other compounds of similar chemical composition and is interpreted as arising from the presence of water molecules coordinated to the same metal cation. The Raman and IR spectra of these compounds have been interpreted in a manner based on the known structure of CaSO₄·2H₂O, which is isostructural with the weinschenkite-type compounds.The Raman and IR spectra of rhabdophane-type LnPO₄·H₂O is analyzed on the basis of the knowledge of the space group of rare earth orthophosphates rhabdophane-type. Its relation with the spectra of rare earth orthophosphates weinschenkite-type is discussed.     

Vibrational spectra of rare earth bromate nonahydrate crystals

Polarized Raman spectra of lanthanum and neodymium bromate nonahydrate crystals and IR spectra in a powdered sample have been observed from 30–4000 cm^?1. Observed Raman bands are experimentally classified into three active symmetry species. The vibrational assignment is made by comparing the spectra of these nonahydrates with those of the corresponding nonadeuterates and similar crystals containing various rare earth ions. From a comparison of the Br-O stretching and lattice vibrations, the binding character between the rare earth ions and ligands is discussed. This consideration is consistent with the result supposed from the lanthanide contraction.     

Vibrational and thermal characterization of Nafion membranes substituted by alkaline earth cations

The vibrational spectra of Nafion^® membranes with alkaline earth cations as counterions have been obtained by photoacoustic infrared spectroscopy (PAS-IR) and Fourier transform Raman spectroscopy (FT-Raman). The symmetrical stretching band of the sulfonate group (∼1060 cm⁻¹) decreases with increasing atomic mass of the countercation, excepting for Mg²⁺, in both techniques. The thermal behavior of Nafion membranes by means of differential scanning calorimetry (DSC) curves showed a dependence on the water content and a similar profile between Nafion-Mg²⁺ and -Ca²⁺, and between Nafion-Sr²⁺ and -Ba²⁺, for the first scanning curve. An ageing effect was also observed on Nafion by DSC curves. High-resolution thermogravimetry (TG) curves under nitrogen atmosphere showed similar decomposition profiles. It was determined from TG curves that there is a decreasing water content with increasing ionic radius of cation, and the thermal stability increasing from Nafion-Mg²⁺ to -Ba²⁺.     

XPS spectra of some transition metal and alkaline earth monochalcogenides

The first-row transition-metal monosulfides and alkaline-earth chalcogenides were studied by means of X-ray photoelectron spectroscopy. It is shown that the bonding in the alkaline earth compounds is relatively ionic with XPS evidence for significant charge separation. On the other hand, transition metal sulfides, with the exception of MnS, appear to be principally metallic with little or no charge separation. Values for the inner orbital binding energy shifts are reported for a large number of monochalcogenides.     

Mass spectra of refractory mixed-oxide compounds which contain an alkaline earth

The mass spectra of the high-temperature vapors over a series of barium tungstates have been measured. It is shown that the dominant vapor species over these mixed oxides is BaO(g); Ba(g) also is present as a minor vapor species over some of these oxides. The spectrum for Ba₂CaWO₆ shows Ca(g) in addition to BaO(g) and Ba(g). It appears that the BaO is formed by the solid state dissociation, e.g.

     

Microwave rotational spectra of alkaline earth monohalides: CaI and BaI

Rotational spectra in the ²Σ⁺ ground state of CaI and BaI have been measured in the 100 GHz range. Precise Dunham coefficients Y_ik and potential constants a_i can be derived from these spectra. Effects of unresolved hyperfine structure have to be considered in the interpretation of the observed γ-splitting.     

Vibrational spectra of mesitylene

Conclusions The Raman spectra of liquid mesitylene and the IR spectra (4000-100 cm^–1) of liquid and gaseous mesitylene were studied. An assignment of the frequencies according to the symmetry and the form of the vibrations is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2265–2270, October, 1982.     

Vibrational spectra,normal coordinates and infrared intensities of four isotopic phenyl acetates

The i.r. and Raman spectra of phenyl acetate and its deuteromethyl and deuterophenyl derivatives have been recorded. The fundamental frequencies of the four isotopic species have been assigned by referring to the Raman depolarization ratios and isotopic frequency shifts. The normal coordinates have been calculated on the basis of a valence force field. The general valence type force constants have been refined by the least-squares method. The i.r. spectra of the four isotopes have been simulated by using the obtained force field in combination with a suitable set of the atomic charges and their fluxes.     

Vibrational spectra of hexamethylcyclodisilazane

The synthesis and ring cleavage reactions of 2-alkyl-2-trimethylsilylmethyl-1.3-dithianes are described. The cleavage lead to 2-alkylthio-1-vinylsilanes and, via silicon migration, to 2-[3-alkylthio-3-(trimethylsilyl)propylthio]-1-alkenes.     

Vibrational spectra of isocyanocyclopropane

Infra-red spectra of isocyanocyclopropane have been measured from 4000 to 400 cm⁻¹ in the vapour and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. A vibrational assignment of all fundamentals is proposed, which is in accord with those of structurally related molecules. Comparison with the vibrational spectra of cyanocyclopropane and cyclopropylacetylene shows the presence of a sizeable inductive effect of the nitrogen atom in isocyanocyclopropane.     

Vibrational spectra of diethylsulfoxide

FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO- and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3-21G* levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole-dipole and hydrogen bonding mechanisms.     

Vibrational spectra of polyacetylenes

A considerable amount of information about optical and electronic properties of polyacetylenes has been obtained during the last decade from vibrational spectroscopy. In this lecture several basic points not yet fully understood will be discussed and a new method for evaluating the vibrational density of states for random defects will be presented.     

Vibrational spectra of indole

Polarized i.r. spectra of partially oriented indole crystals grown from the melt between pressed salt plates and the Raman spectra of the melt and polycrystalline indole are reported. Some fundamental vibrational assignments and the manifestations of the NH ⋯ π interaction in the vibrational spectra are discussed.     

Vibrational spectra of dipropylsulfoxide

FTIR and Raman spectra analysis of pure dipropylsulfoxide (DPSO), binary mixtures of DPSO/CCl(4), and DPSO/water has been first performed. The complex pattern of spectra has been explained on the basis of molecular interactions between DPSO and other molecules and, in the aqueous solutions, the role of both hydrophilic and hydrophobic interactions have been discussed depending on the concentrations. The changes in the intensities and in the frequencies of DPSO bands on concentration have been considered. The curve fitting procedure has been performed for both SO and C-H stretching region, and, on the basis of deconvolution results different type of molecular interactions have been considered. Density function theory DFT/(B3LYP) method has been used to determine the optimized geometry for free DPSO and for 1 DPSO:1 water complex. On the basis of the 6-31+G(d) quality sets parameters, the DFT calculated bond parameters and harmonic vibrations are in a very good agreement with experimental data.     

Vibrational spectra of 2,2-dichlorobutane

IR and Raman spectra were obtained for 2,2-dichlorobutane, which was found to exist in two molecular conformations. Normal coordinate calculations were made for 2,2-dichloropropane and both conformers of 2,2-dichlorobutane.