Zh. Nickolov

Raman and IR study of cobalt acetate dihydrate

Abstract The Raman spectra in the region 40–3800 cm−1 and the IR spectra in the region 400–4000 cm−1 of cobalt acetate dihydrate (CADH) have been studied and compared to the corresponding spectra of cobalt acetate tetrahydrate (CATH). Spectral information on the existence of two different acetate ions in the lattice of CADH has been derived and some suggestions about the nature of the acetate groups and water molecules in the crystal have been put forward.

Raman study of complexation in aqueous solutions of magnesium acetate

Abstract Raman spectra of aqueous solutions of magnesium acetate at 293 K have been studied in the concentration range 0.65–3.24 M, as have the Raman spectra of the crystallohydrate Mg(CH 3 COO) 2 ·4H 2 O. Fourier deconvolution and band fitting techniques have been used to analyse the spectra in three characteristic regions. The gradual evolution of two new components, in addition to the component corresponding to the CC vibration of the free acetate ion, is observed in the CC region of the solutions. These are identified as belonging to mono- and bisacetato complexes. In saturated solutions the bisacetato complexes are the dominating metal-ligand species. Their presence is confirmed also by Fourier deconvolution of the in-plane rocking CO 2 vibration.

Concentration Raman study of intramolecular, intermolecular and Fermi resonance interactions in the OH stretching spectra of dilute solutions of HDO in D2O using Fourier deconvolution technique

The Raman OH stretching spectra of dilute solutions of H20 in D20, from 100 mole per cent to 10 mole per cent concentration, are studied. For the first time the decoupled OH spectra are treated by means of Fourier deconvolution technique. The resolved components in the isotropic and anisotropic spectra are analysed in terms of a model. The frequency and intensity behaviour of the components confirm the suggestion, that strong decoupling of all vibrations with dilution takes place. It is shown that intramolecular and Fermi resonance interactions are negligibly small under 20 mole per cent concentration. On the contrary, a significant intermolecular interaction, with a coupling constant equal to 42 cm−1, is observed down to concentrations of 10 mole per cent. The latter is explained with the significant number of the HDO molecules, which have at least one HDO, or H20 neighbour at this concentration. In respect to intermolecular interaction a dilution of H20 in D20 down to 10 mole per cent concentration is e...

Determination of Salts in Water Solutions by a Skewing Parameter of the Water Raman Band

The investigations of the Raman scattering from water show that information about the water temperature and the concentration of the dissolved salts is encoded in the band shape of the O-H stretching region 2800–3800 cm−1.

Concentration-dependence studies of Raman spectra of water by the method of self-deconvolution

Abstract The method of self-deconvolution is applied in Raman spectroscopy. The advantages provided by the polarized nature of the scattered light are discussed. The behaviour of the components in the composite Raman spectrum of water (OH-stretching region) versus the concentration of dissolved NaI and NaClO 4 salts is investigated. Effects which are impossible to observe by the widely used fitting procedures are also reported.

Determination of Fluorescence Quantum Yields Using a Spontaneous Raman Scattering Line of the Solvent as Internal Standard

Abstract A method for determination of molecular quantum yields of fluorescent compounds in solution by internal calibration with the signal of spontaneous Raman scattering of the solvent is proposed. An experimental verification of the method is carried out for substances with known quantum yields and satisfactory agreement between experimental results and literature values is obtained.

Application of laser induced saturation of molecular fluorescence for lifetime measurements

Abstract A technique for the determination of fluorescence lifetimes based on the laser induced saturation of molecular fluorescence is described. It allows lifetime measurements using exciting laser pulses longer than the lifetime under determination. The range of applicability of the technique is discussed and an experimental verification is carried out.

Raman study of 12-crown-4, 15-crown-5, 18-crown-6 and their complexation with metal cations using Fourier deconvolution of CH stretching spectra

Abstract The Raman CH stretching spectra of 12-crown-4, 15-crown-5 and 18-crown-6 and their complexes with some metal cations— Li+, Na+, K+ and Cu+ in water solutions are studied. For the first time Fourier deconvolution is applied to resolve the overlapped components in the corresponding isotropic and anisotropic spectra. A model is introduced which explains the variety of components in the spectra by means of splitting of the unperturbed CH stretching frequency owing to intramolecular interactions and Fermi resonance. The coupling constants of these interactions, as well as all parameters according to the model, are calculated for studied crowns and their complexes. The differences in the number and intensity of the resolved components in the spectra of the various crowns are explained with the corresponding differences in the coupling constants and model parameters. It is established that complexation leads to some increase in the unperturbed stretching frequency, probably owing to the increase in strain of the crown molecule. It is concluded that 15-crown-5 forms 2:1 and 1:1 complexes with K+ and Na+ cations respectively and 12-crown-4 forms a 2:1 complex with the Na+ cation.

Fluorescence of the benzophenone ketyl radical: solvent effects

Abstract The fluorescence of the benzophenone kethyl radical (BKR) was studied in different solvents by a double-pulse excitation technique using two synchronized lasers. Fluorescence quantum yields of the BKR were determined employing a new technique suitable for measurement of short-lived transients with low level emission. By analysing the fluorescence spectral shape and the values of the quantum yields in the different solvents it can be concluded that charge transfer complexes are formed in the excited doublet state of BKR, with the molecules of the solvents exibiting electron-donor properties.

Raman Temperature Study of 12-Crown-4 Using Fourier Deconvolution of CH Stretching Spectra

Abstract The Raman CH Stretching spectra of 12C4 in water solution, for temperatures from 5 to 80 °C, are studied. For the first time, Fourier deconvolution technique is applied to resolve the overlapped components in the corresponding isotropic and anisotropic spectra. The results are treated by means of a model. explaining the variety of resolved components with a splitting of the unperturbed CH stretching vibration. owing to intramolecular interactions. The temperature behaviour of the coupling constants of these interactions is discussed.