Biomedical subjects

G B Furman

Publications and source records attributed to G B Furman.

5 recordsLinked to original sources

PubMed2005

Dynamics of multiple quantum coherences in dipole-coupling spins in solid.

A perturbation method deals with dipolar coupling spins in solids is presented. As example of application the method, the multiple-quantum coherence dynamics in clusters of a linear chain of four nuclear spins and a ring of six spins coupled by dipole-dipole interaction are considered. The calculated 0Q and 2Q intensities in a linear chain of four nuclear spins and 6Q intensity in a ring of six spins vs. the duration of the preparation period agree well with the exact solutions (for linear chain of four nuclear spins) and simulation data (for linear chain of four nuclear spins and a ring of six spin).

Journal Article↗

PubMed2000

Spin diffusion of dipolar energy in NQR.

The theory of spin diffusion was extended to the case of nuclear dipolar order in solids containing paramagnetic impurities and nuclei with spin I > 1/2 having nuclear quadrupole moment. We show that spin diffusion process of dipolar order takes place in solids containing paramagnetic impurities. At the start of relaxation process, the direct relaxation regime is realized with non-exponential time dependence. Then the relaxation regime will be changed to diffusion-limited one. Using obtained expressions for the spin lattice relaxation times for these two relaxation regimes, the diffusion coefficient of the dipolar order in nuclear quadrupole resonance can be estimated from experimental data.

Chemical Phenomena↗

PubMed1999

Spin diffusion and nuclear spin-lattice relaxation in irradiated solids: a multiple-pulse NQR study.

We present a detailed theoretical and experimental NQR multiple-pulse spin-locking study of spin-lattice relaxation and spin diffusion processes in the presence of paramagnetic impurities in solids. The relaxation function of the nuclear spin system at the beginning of the relaxation process is given by exp (-t/T1rho)alpha, where T1rho is spin-lattice relaxation time in rotating frame and alpha = d/6, d is the sample dimensionality. Then the relaxation proceeds asymptotically to an exponential function of time, which was attributed to the spin-diffusion regime. Using the experimental data obtained from the analysis of those two relaxation regimes in gamma-irradiated powdered NaClO3, spin diffusion coefficient has been determined and the radius of the diffusion barrier has been estimated.

Electron Spin Resonance Spectroscopy↗

PubMed1998

Spin-locking in one pulse NMR experiment.

The response of a spin system to a long (in comparison to spin-spin relaxation time T2) radiofrequency pulse has been studied. We observed that the magnetization after the long pulse does not fall to zero at time t >> T2 for both on-resonance and off-resonance conditions. The dependencies of the magnetization on frequency offset, linewidth and radiofrequency power are investigated, both theoretically and experimentally. The question of the effective field direction is also discussed.

Humans↗

PubMed1995

Fractional power time dependence of the nuclear magnetization in the presence of paramagnetic impurities.

We extend the theory of growth of the nuclear magnetization in the presence of paramagnetic impurities and the absence of spin diffusion to the case of multi-paramagnetic centers. We show that for short times after saturation pulses, the rate of growth of the magnetization is proportional to t alpha where t is the time and alpha = 1/3, 1/2 and 2/3 for one-, two- and three-dimensional systems, respectively. We also present experimental data for which the total time-dependent magnetization is proportional to exp[-(t/T1) alpha], which reduces to the above time dependence for short times.

Electron Spin Resonance Spectroscopy↗