Spectrochimica Acta最新文献

The frequency ratio of the ν₁(A₁′) and ν_t2(E′) vibrations of the CS₃²⁻ ion in trithiocarbonates was observed to assume values below as well as above unity, depending on the crystal field and, probably, on bond interactions between metal and sulfur.

Urey-Bradley force constants, Coriolis coupling coefficients, and mean amplitudes of vibration were calculated for the CS₃²⁻ ion from infra-red and Raman spectroscopic data. The force constants are in accordance with orbital valence force field values. The calculated values for the coupling coefficients and the vibration amplitudes were found to be very similar to the corresponding values for BCl₃.

The infra-red spectra of 19 molybdates and 18 tungstates have been measured from 4000 to 250 cm⁻¹. The identity of the samples was confirmed by X-ray powder diffraction. The spectra are generally sufficiently individual in detail to permit identification of the particular substance. The results are discussed in terms of the site symmetry of the anionic group.

The infrared spectra of the ten isomeric dimethyl naphthalenes and the two monomethyl naphthalenes have been observed in the CH stretch, 2000-1650 and the 700-400 cm⁻¹ regions. The effect on the aromatic CH stretching vibrations due to the position of the methyl groups on the naphthalene nucleus is outlined. The position of the methyl groups can be established from data obtained from the 2000-1650 and the 700-400 cm⁻¹ regions. Effect on band frequencies and intensities by replacement of methyl by phenyl group in the monosubstituted naphthalene is discussed.

The force constants of the general valence force field (GVFF) are calculated with a new method for several oxo-anions with T_d-symmetry.

Stimulated Raman spectra have been excited from a large number of molecules. The most intense lines arising from conventional Raman transitions predominate. However, for the compounds chloroform and bromoform, a polarized line which is not the strongest line in the conventional Raman spectrum is amplified in the stimulated Raman effect.

The infra-red spectrum of DNCO has been examined over the range 3000-400 cm⁻¹ under medium resolution. The six fundamentals have been observed and assigned as follows: ν₁, 2634·9 cm⁻¹; ν₂, 2235 cm⁻¹; ν₃, 1310 cm⁻¹; ν₄, 460 cm⁻¹; ν₅, 766·8 cm⁻¹ and ν₆, 602·9 cm⁻¹. The fundamentals ν₄ and ν₅ interact by Coriolis coupling with ν₆ it has been determined that their unperturbed frequencies would be 468·5 and 758·3 cm⁻¹ respectively. It was found that A″ = 17·3 ± 0.1 cm⁻¹ and B̃″ = 0·3405 ± 0·0007 cm⁻¹.

Infrared and Raman data were used to assign the vibrational spectrum of trimethyl phosphite. The assignment was aided by comparison of the infrared and Raman data for trimethyl phosphite with the known infrared and Raman data and assignments for phosphorous triflouride and trimethyl phosphate.

The interpretation of the experimental data suggest that the symmetry of trimethyl phosphite could be less than C_3υ or C₃.

A tentative correlation is suggested for ν_sym.P(-O-)3 in phosphites and phosphates.

Bond orientations in uranyl nitrate hexahydrate have been measured using polarized infra-red radiation and the technique of attenuated total reflection. The technique of using polarized radiation with attenuated total reflection is discussed and the results used to produce a model in agreement with X-ray data.

A method using a single spectral line for determining simultaneously the distribution of atoms in two different levels of energy and consequently the radial distribution of temperature in a d.c. arc has been worked out.

The principles of this method are as follows:

Two transverse images—one above the other—of the light source are formed on the slit of a spectrograph by means of illuminations systems describe. In one the images the arc in addition is uniformly illuminated from behind by its own radiation. By means the intensity distribution along the same spectral line in both images the radial distribution of the module of extinction (extinction per unit length), which is proportional to the concentration of atoms in the ground state of energy, as well as the radial distribution of emission coefficients (true radiation intensity per unit length), which is proportional to the concentration of atoms in the excited state belonging to the spectral line in question, can be determined. Finally the radial distribution of temperature in the light source can then be calculated.