Formation Mechanisms of Single-Pulse and Secondary Echoes in Systems with a Large Inhomogeneous Broadening of NMR Lines

In the frames of Mims transformation matrix method the equation for nuclear magnetization are obtained describing the dynamics of nuclear spin-systems with a strong Larmor and Rabi inhomogeneous broadenings of NMR line in conditions of their unequlibrium earlier obtained by the statistical tensors method. As example, properties of proton single-pulse echo and its secondary signals in probe material (silicon oil) coated on the surface of high-Tc superconducting-oxides powder and in metallic hydride are presented.Comment: 7 pages, 5 figure

Investigation of multiple echo signals formation mechanism in magnet at excitation by two arbitrary radio-frequency pulses

The quantum-mechanical calculations of intensities and time moments of appearance of multiple spin echo signals of excitation of nuclear spin system of magnet by two arbitrary width radio-frequency pulses were carried out. This method was used by us earlier at consideration of multiple-pulse analogs of single-pulse echo in multidomain magnets upon sudden jumps of the effecting magnetic field in the rotating coordinate system during the action of radio-frequency pulse. The formation mechanisms of echo signals are discussed. The appearance of four primary stimulated echo signals is predicted. The total number of echo signals at fixed parameters of radio-frequency pulses does not exceed thirteen ones. Theoretical conclusions are in compliance with experiments carried out on lithium ferrite. As it was established by us earlier in this magnetic dielectric, in difference from ferrometals, it is observed very short relaxation times of single-pulse and two-pulse stimulated echoes, and the contribution of radio-frequency pulse fronts distribution mechanism is insignificant. For this reason lithium ferrite is a good material for the experimental verification of theoretical conclusions in experimental conditions most close to the theoretical model.Comment: 16 pages, 5 figures, 1 tabl

Relaxation oscillations of Zeeman and dipole magnetizations of a paramagnet under conditions of deep low-frequency modulation

The relaxation oscillations of Zeeman and dipole magnetizaions in spin system of a solid paramagnet are theoretically analyzed under conditions of intermediate saturation of magnetic resonance and strong low-frequency modulation of the external magnetic field. Peculiarities of the relaxation oscillations in the synchronous detection regime are considered.Comment: 15 page

Hydrogen ordering influence on the proton spin-lattice relaxation time in metal-hydrogen compoun Hydrogen ordering influence on the proton spin-lattice relaxation time in metal-hydrogen compounds

Results of the experimental study of ordering lanthanum hydrides of LaHX system are presented. It is shown that obtained results can be interpreted as an indirect confirmation of the existence of order-order transformations in LaH2+c hydrides.Comment: 14 page

Single-pulse and two-pulse echoes at multipulse excitation mode in multidomain magnetic materials

Properties of single-pulse and two-pulse echoes and their secondary echo signals as well as the role of reversible relaxation in the observed decays of echo signals at the multipulse excitation mode in a number of multidomain magnetic materials were studied.Comment: 12 pages, 9 figures. To be published in Phys.Letters

Influence of pulsed magnetic field on single- and two-pulse nuclear spin echoes in multidomain magnets

By the method of additional pulsed magnetic field influence in different magnetic materials (half metals, manganites, lithium ferrite, cobalt) it is established the analogy of time diagrams of magnetic pulse influence on single- and two pulse echoes in magnets when the distortion mechanism of single-pulse echo formation is effective, and the absence of such analogy in the case of lithium ferrite where the multipulse mechanism of single-pulse echo formation is effective. It is shown also that the timing and frequency diagrams of magnetic pulse influence on the two-pulse echo signals, corresponding to the symmetric and asymmetric magnetic pulse applications in the studied magnets, are defined by their domain walls parameters and could serve for their qualitative and quantitative characterization.Comment: 11 page

The vacuum thermal treatment effect on the optical absorption spectra of the TiO2 coated by Ni-B nano-clasters photocatalyst powders

The thermal vacuum treatment effect on the optical absorption spectra of the TiO2 nanopowders, both pure and coated by the Ni-B clasters with the original electroless method was investigated. It was observed that the thermal treatment of pure TiO2 nanopowders does not change their optical absorption spectrum while after the coating of these powder particles by the Ni-B clasters the thermal treatment results in the increase of the optical light absorption in the visual region of spectrum. This points to the possibility of the significant improvement of the photocatalist efficiency of TiO2 nanopowders coated by the Ni-B clasters using the thermal treatment.Comment: 8 pages, 4 figure

Formation mechanisms and relaxation of NMR spin-echo signals excited by two arbitrary duration radio-frequency pulses in magnets

The work is devoted to the problem of multiple signals of nuclear spin echoes in magnets, excited by a series of radio-frequency (RF) arbitrary duration pulses exceeding the free induction decay time. The quantum-statistical approach based on the Liouville equation solution for the statistical operator of system is developed for the investigation of echo-processes. The obtained theoretical results for the number of echo signals, time moments of their formation and their intensities are in good agreement with experiments carried out on magnets (ferrites, ferrometals, half metals, manganites). The pointed approach is general and could be applied to EPR and NQR, which is interesting also for its application for remote detection of explosives and narcotics. The application of wide RF pulses and their sequences makes it possible to accumulate weak signals, enriches the echo-response spectrum with clearly separated intensive lines, i.e. essentially increases the sensitivity of apparatus and, correspondingly, the possibilities to explore the fine details of dynamical and relaxation processes taking place in nuclear spin-systems with sufficiently long relaxation times. The work contains also results of new experiments on study of relaxation processes in these systems.Comment: 8 pages, 2 figure

Peculiarities of timing and spectral diagrams of magnetic video-pulse excitation influence on NMR spin-echo in magnets

We present the first systematic study of timing and spectral diagrams of magnetic video-pulse influence on the NMR two-pulse echo in a number of magnets (ferromagnets, ferrites, half metals, intermetals). It is shown that the timing diagrams showing the dependence of two-pulse echo intensity on the temporal location of a magnetic video-pulse in respect to radio-frequency pulses and the spectral diagrams of this influence are defined mainly by the local hyperfine field anisotropy and domain walls mobility. These diagrams could be used for the identification of the nature of NMR spectra in multidomain magnetic materials and to improve the resolution capacity of the NMR method in magnets.Comment: 9 page

Ternary complexes of albumin-Mn(II)-bilirubin and Electron Spin Resonance studies of gallstones

The stability of albumin-bilirubin complex was investigated depending on pH of solution. It was shown that the stability of complex increases in presence of Mn(II) ions. It was also investigated the paramagnetic composition of gallstones by the electron spin resonance (ESR) method. It turned out that all investigated gallstones contain a free bilirubin radical-the stable product of its radical oxidation. Accordingly the paramagnetic composition gallstones could be divided on three main types: cholesterol, brown pigment and black pigment stones. ESR spectra of cholesterol stones is singlet with g=2.003 and splitting between components 1.0 mT. At the same time the brown gallstones, besides aforementioned signal contain the ESR spectrum which is characteristics for Mn(II) ion complexes with inorganic compounds and, finally, in the black pigment stones it was found out Fe(III) and Cu(II) complexes with organic compounds and a singlet of bilirubin free radical. It is supposed that crystallization centers of gallstones could be the polymer network of bilirubin radical polymerization in complex with different metal ions earlier discovered in gallstones.Comment: 12 pages, 6 figure