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Kaliningrad, Russia

Sinyavsky N.,Baltic State Academy | Dolinenkov P.,Immanuel Kant Baltic Federal University | Kupriyanova G.,Immanuel Kant Baltic Federal University
Applied Magnetic Resonance | Year: 2014

The paper describes the results of an experimental study of the 35Cl and 14N nuclear quadrupole resonance in composite and porous materials, the influence of the environment and the crystallite size of powder on the nuclear quadrupole resonance line widths, as well as on the spin-spin and spin-lattice relaxation times. It is established that the spin-lattice relaxation time has a unimodal distribution, and the spin-spin relaxation time-bimodal distributions for all the investigated samples. The idealized distribution function of the relaxation times is obtained on the assumption that the concentration of inhomogeneities and relaxativity decreases with an increasing distance from the surface into the interior of the crystallite exponentially. It is shown that the model with the spin diffusion explains the shortening of the decay signal with decreasing grain size, but this is not confirmed by the experimental distribution of relaxation times obtained by means of the inverse Laplace transformation. © 2014 Springer-Verlag Wien. Source

Glotova O.,Adam Mickiewicz University | Sinyavsky N.,Baltic State Academy | Jadzyn M.,Adam Mickiewicz University | Ostafin M.,Adam Mickiewicz University | Nogaj B.,Adam Mickiewicz University
Applied Magnetic Resonance | Year: 2010

The method of random sampling was introduced for the first time in the nutation nuclear quadrupole resonance (NQR) spectroscopy where the nutation spectra show characteristic singularities in the form of shoulders. The analytic formulae for complex two-dimensional (2-D) nutation NQR spectra (I = 3/2) were obtained and the condition for resolving the spectral singularities for small values of an asymmetry parameter η was determined. Our results show that the method of random sampling of a nutation interferogram allows significant reduction of time required to perform a 2-D nutation experiment and does not worsen the spectral resolution. © 2010 The Author(s). Source

Sinyavsky N.,Baltic State Academy | Dolinenkov P.,Immanuel Kant Baltic Federal University | Mackowiak M.,Polish Academy of Sciences
Solid State Nuclear Magnetic Resonance | Year: 2012

The experiment with phase inversion and phase-inverted echo-amplitude detected nutation (PEANUT) was introduced in the nuclear quadrupole resonance (NQR). Formulas were obtained describing the NQR (I=3/2) experiment. Exemplary experiments are provided confirming the predicted particularities of the PEANUT spectra in NQR Cl-35. It is proposed to apply the method for the purpose of determination the asymmetry parameter of the electric field gradient (EFG) tensor in powders with the help of the analysis of PEANUT interferograms. Application of two-dimensional PEANUT experiments, in which the nutation frequencies correlate with the resonance NQR frequencies, can substantially simplify the interpretation of complex spectra. © 2012 Elsevier Inc. All rights reserved. Source

Mackowiak M.,Polish Academy of Sciences | Sinyavsky N.,Baltic State Academy
Solid State Nuclear Magnetic Resonance | Year: 2010

The effects of off-resonance irradiation in 2D exchange NMR at zero-field are analysed. A theoretical treatment of the 2D exchange NMR pulse sequence is presented and applied to the quantitative study of exchange processes in molecular crystals. It takes into account the off-resonance irradiation, which critically influences the spin dynamics. The response of a system of spins I=3/2 in zero applied field to the three-pulse sequence is analysed. The mixing dynamics by exchange and the expected cross-peak intensities as a function of the frequency offset has been derived. It is shown that the off-resonance effects are of crucial importance for the quantitative description of the exchange spectra. The theory is successfully tested for the exchange spectra of hindered trichloromethyl groups of p-chloroanilinium trichloroacetate, where the conventional approach without taking into account the off-resonance phenomena has failed. © 2010 Elsevier Inc. All rights reserved. Source

Sinyavsky N.,Baltic State Academy | Mozzhukhin G.V.,Gebze Institute of Technology | Dolinenkov P.,Immanuel Kant Baltic Federal University
NATO Science for Peace and Security Series B: Physics and Biophysics | Year: 2014

The influence of the size effect of the crystallites in powders on the form and width of spectral lines, on the spin-spin and spin-lattice relaxation parameters of the nuclear quadrupole resonance (NQR) of 14N nuclei in sodium nitrite was studied. It was established that a decrease of the average crystallite size produces the widening of the NQR lines and the shortening of the relaxation times in the direct method of NQR detection. It was supposed that these are the results of the spin-spin diffusion process. A multi-exponential inversion of the decays of the longitudinal and transverse components of the nuclear magnetization was used to obtain the distribution of relaxation times. © Springer Science+Business Media Dordrecht 2014. Source

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