Raman spectra of crystalline double sulphates

Raman spectra of single crystals of K₂M(SO₄)₂ · 6 H₂O where M=Mg, Zn, Ni or Co have been recorded for the first time usingλ 2537 as the exciting radiation. The corresponding five single sulphates have also been studied. Interesting results concerning the substitution of magnesium, zinc, nickel or cobalt in the double sulphate lattice on the sulphate frequencies are observed. The lattice spectra of these double sulphates are analysed group theoretically and discussed in relation to the lattice spectra of the corresponding individual sulphates. Certain new results concerning the Raman spectra of the individual sulphates have also been obtained and in the case of CoSO₄ · 7 H₂O the spectrum has been recorded for the first time.     

Electron-energy-loss spectroscopy of C60 monolayer films on active and inactive surfaces

The characteristics of interaction between C₆₀ molecules and Si(1 1 1)-7×7, Ag/Si(1 1 1)-√3×√3 R30° and layered material MoS₂ surfaces have been investigated using electron-energy-loss spectroscopy (EELS). The EEL spectrum of C₆₀/Si(1 1 1)-7×7 shows a new peak at loss energy of 2.7 eV. This indicates the existence of charge transfer from the substrate to C₆₀ molecules. The EEL spectrum of a C₆₀ monolayer film grown on a cleaved surface of MoS₂ is almost the same as that of bulk C₆₀. The EEL spectrum of a C₆₀ monolayer film on an Ag/Si(1 1 1) surface is quite different from that on a clean Si(1 1 1)-7×7 surface, although the films on those substrates have the same epitaxial arrangement. Furthermore, intensities of energy-loss peaks of C₆₀/Ag/Si(1 1 1) are slightly smaller than those of C₆₀/MoS₂ in spite of having the same loss-energy. This suggests that the interaction between C₆₀ molecules and the Ag/Si(1 1 1) surface is stronger than that between C₆₀ molecules and the MoS₂ surface.     

High pressure raman spectra of crystalline sulfur

Abstract

Well—resolved Raman spectra of crystalline sulfur have been recorded in a diamond anvil cell (DAC) in the pressure range from atmospheric pressure to 50 GPa at room temperature, using an 0.6 m triple spectrograph and a CCD multichannel detector. The spectra indicate two phase transitions in the pressure region between 10 and 15 GPa.     

Electron-energy-loss and X-ray photoelectron spectra. Part 1. Electronic structure of tetraphenylporphyrin and its nickel derivative

Specific information on the energy level diagram and on the energy forbidden gap of tetraphenylporphyrin and its Ni derivative has been obtained by means of electron energy-loss spectroscopy (EELS) and X-ray photoelectron spectroscopy techniques. Comparison of the free ligand and its metal derivative emphasizes the importance of the metal 3d levels in the conduction processes. The interband and plasmon transition present in the EELS spectra of these species are compared with the theoretically calculated energy level diagram and experimental data.     

Raman spectra of crystalline iron perchlorate hexahydrate

Raman studies of crystalline iron perchlorate hexahydrate (Fe(ClO₄)₂·6H₂O) in the region of lattice and anion internal modes were carried out in the temperature range 80–385 K. The temperature‐dependent Raman results are consistent with those from previous works, showing that two phase transitions occur around 336 and 245 K. The transition at 336 K may be considered as an order–disorder transformation, while the one at 245 K is associated with the configurational disorder of the tetrahedron of the perchlorate ions. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigation of RS spectra of crystalline potassium perchlorate

The processes of molecular relaxation in crystalline potassium perchlorate are investigated by the method of RS spectroscopy in the field of totally symmetrical oscillation v₁(A) of the amen ClO ₄ ⁻ . The parameters of reorientation in relation to the polarized RS lines are evaluated from the temperature dependences of line widths. It is established that in KClO₄ the reorientation represents the activation process. Time correlation functions are obtained and the times of vibrational and orientational relaxation are determined, which show that with an increase in temperature the contribution of homogeneous broadening increases while that of the inhomogeneous one remains practically unchanged. Kh. I. Amirkhanov Institute of Physics at the Dagestan Center of the Russian National Academy of Sciences, 26 Bakinskikh Komissarov St., 94, Makhach-Kala, 367003. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 932–935, November–December, 1998.     

Vibrational spectra of crystalline potassium ferri- and ferrocyanide

The IR spectra of the crystalline salts K₃[Fe(CN)₆] (I) and K₄[Fe(CN)₆] (II) have been studied in the 1600–5000 cm^–1 range for the purpose of investigating the spectral difference in the valence states of the central atoms of the complex anions. The appearance of the doublet structure of thev ₆ band in the spectrum of salt II is due to distortion of its anion to D_4h symmetry. The vibrational spectra of both salts are interpreted.In conclusion, I should like to express ray sincere appreciation to Academician A. N. Terenin for his guidance and to L. A. Grivov and D. S, Bystrov for their valuable comments.     

Stray-light induced artefacts in absorption spectra of crystalline oligothiophenes

The absorption spectra of oligothiophene single crystals and thin films are discussed in terms of stray light induced experimental artefacts. After typical experimental problems have been overcome, absorption spectra can be collected over a wide spectral range in the UV-Vis region that has often not been included in the literature data. A clear similarity is found between the absorption spectra of single crystals and highly ordered thin films. Received 10 April 2002 Published online 13 August 2002