Porous silica materials offer wide range of possibilities for enhancement of the productivity of oil reservoirs. However the mechanism of adsorption of polar components of crude oil on silica surface is poorly understood that hinders technological improvement of supports and oil extraction. We have synthesized opal films with the silica microspheres size of about 360 ± 20 nm, specific surface area of 5.2 m² × g⁻¹ and pore size of 230 nm. We have fractionated and characterized oil and oil asphaltenes from heavy (Ashalchinskoe) oil. By pulsed electron paramagnetic resonance (EPR) and double electron nuclear resonance (ENDOR) in the W-band frequency range (microwave frequency of 94 GHz, magnetic field of 3.4 T) we have studied the adsorption of oil asphaltenes on the surface of opal samples using the intrinsic for asphaltenes paramagnetic vanadylporphyrins (VO) complexes. ¹H ENDOR spectra are found to be different for initial and the adsorbed samples in their central parts (that is a sign of asphaltenes VO disaggregation) whereas no significant changes in the W-band EPR spectra were detected. Contrasting to alumina support, no strong electron proton interaction with the protons on the surface of SiO₂ (presumably, silanol groups) was found and infiltration of the oiled opal films with gasoline changes the central part of ¹H ENDOR spectra. It shows that the proton containing groups on the surface of amorphous SiO₂ sample can significantly change the asphaltene adsorption properties and ENDOR of the intrinsic for oil paramagnetic centers could be used for the characterization of surface state in porous media in situ or operando.

The phospho-silicate glass containing 10 mol% CrF₂ was studied by electron paramagnetic resonance (EPR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) equipped with electron diffraction apparatus which is specified for measuring the electron diffraction pattern (EDP). EPR spectroscopy offers information about oxidation states of Cr ions and their coordination symmetry in the vitreous network. The EPR spectra of Cr³⁺ of glass containing 10 mol% CrF₂ have revealed two essential resonance signals with effective g values at g_eff = 4.93 and g_eff = 2.14. Presence of the two resonances is considered as a good evidence for the presence of trivalent chromium ions of octahedral coordination in glass containing 10 mol.% CrF₂. X-ray and electron diffraction measurements on sample containing 10 mol% CrF₂ have confirmed that there are some crystalline phases distributed in the main glass network. TEM micrograph has revealed a heavy accumulation of crystalline species. The glass which was exposed to irradiation process has showed different EPR signal when it compared with that of unirradiated sample.

The magnetic nuclear spin-lattice relaxation has been studied in PrF₃. It was found that ¹⁴¹Pr spin lattice relaxation rate is untypically high for the Van Vleck insulator. According to all existing experimental data the only relaxation channel for enhanced nuclear moments at low temperatures is interaction with paramagnetic impurities and typical nuclear relaxation rate in rare earth Van Vleck paramagnets at liquid helium temperatures is 1 s⁻¹. The measured value is 100 s⁻¹. At the assumption that relaxation is caused by the strong 4f-4f cooperative interaction mediated by phonons [1], we measured ¹⁴¹Pr relaxation rates in a number of Pr_xLa_1−xF₃ samples and found that in diluted samples relaxation slows down to the usual for insulators values.

The home-built pulsed nuclear magnetic resonance spectrometer is described, it consists of rather cheap commercial hardware for radio frequency (RF) pulse generation and signal acquisition system. The old-stuff superconducting magnet (9 T) and modified current insert allows to vary first order cold shim gradient fields and the B₀ field in the range of 0-8.5 T. The helium cryostat inserted in a wide bore of the magnet and the sample temperature control system allow to perform nuclear magnetic resonance (NMR) experiments in the temperature range of 1.65-300 K. The software created in Labview development environment synchronizes the RF excitation and acquisition systems and controls the parameters of pulse sequences and data acquisition in the 5-500 MHz range of frequencies. The maximum achieved resolution in ¹H NMR spectra using first order cold shims is ca. 0.5 ppm in a spherical water sample of 5-mm diameter.

 Created at room temperature by X-ray irradiation at the dose of about 5 kGy radiation-induced centers in stable octacalcium phosphate (OCP) powders obtained by double transformation of α-tricalcium phosphate (TCP) are studied by means of pulsed electron paramagnetic resonance (EPR). No EPR signals within the sensitivity of the used equipment in the non-irradiated samples were detected. In the irradiated species complex EPR spectrum signals appeared. Three types of the paramagnetic centers are decomposed in the investigated samples. Their spectroscopic parameters (components of g-factors and hyperfine constants) are defined. Based on the extracted parameters two of them are ascribed to CO₂⁻ and NO₃²⁻ radicals while the nature of the third one is still questionable. The spectroscopic parameters of NO₃²⁻ stable radical is found to be differ than these for TCP or hydroxyapatite. The obtained results could be used for the tracing of the mineralization processes from its initiation to the completion of the final product and for the identification of the OCP phase.

Multiple quantum (MQ) nuclear magnetic resonance (NMR) experiment is considered on chains of fluorine atoms in calcium fluorapatite. The second moments of the line shapes of the MQ coherences on the evolution period of the MQ NMR experiment are calculated analytically in the approximation of nearest neighbor interactions. The calculated values are used for a description of the experimental data with semi-phenomenological formulas assuming that the relaxation of the MQ coherences follows the Gaussian law on the evolution period. A satisfactory agreement with the experimental data is demonstrated.

Dipolar relaxation of multiple quantum (MQ) nuclear magnetic resonance (NMR) coherences on the evolution period of the MQ NMR experiment is investigated experimentally and theoretically in a single crystal of calcium fluorapatite. The theoretical approach is based on the zz model when the flip-flop part of the dipole-dipole interactions is not taken into account. The analytical results obtained in the zz model are compared with the numerical calculations for a chain consisting of 12 spins. The role of heteronuclear interactions of ¹⁹F and ³¹P nuclear spins in the dipolar relaxation of MQ NMR coherences is also investigated. A comparison of the experimental data and the theoretical predictions is discussed.

The functions transforming according to the nonequivalent irreducible representations (IR) Γ'₂, Γ'₃ and Γ'₆, Γ'₇ have been found using the projection operators of the IR D_S of the full rotation group on the subspaces of IR of T, T' and T_h, T'_h cubic groups. With allowance for the properties with respect to the operation of the time reversal sign, the functions are combined into representations Γ'₂₃ and Γ'₆₇ respectively, of twice the larger dimension. Along with the functions transforming according to all other IRs Γ'₁, Γ'₄ and Γ'₅ presented earlier, they will facilitate the consideration of various kinds of effects due to the energy level splitting of rare-earth ions in the crystal electric fields of T, and T_h group symmetry.