Relaxation Processes in NQR Multiple-Pulse Spin-Locking

1986 ◽  
Vol 41 (1-2) ◽  
pp. 366-369 ◽  
Author(s):  
N. E. Ainbinder ◽  
G. B. Furman ◽  
G. E. Kibrik ◽  
A. Yu. Poljakov ◽  
I. G. Shaposhnikov
Keyword(s):  
Time Constant ◽  
Pulse Sequence ◽  
Spin Echo ◽  
Rate Equations ◽  
Relaxation Processes ◽  
Quasi Equilibrium ◽  
Multiple Pulse ◽  
Spin Lattice ◽  
Kinetic Coefficients ◽  
Spin Locking

A theory of the spin-lattice and spin-spin relaxation processes in quadrupole spin systems with I > 1/2 in the situation of the multiple-pulse NQR spin locking is proposed for the pulse sequence MW-4. The theory is based on the assumption that for t ≳ T2 the change of the spin system is a quasi-equilibrium process. Rate equations for inverse generalized temperatures are obtained and the kinetic coefficients calculated for the case o f exponential correlation functions. The above assumption was confirmed for some substances containing the 35Cl and 123Sb, and the time constant T1e characterizing the spin echo signal decay was investigated and compared with the time constant T1q, in the case of continuous spin locking.

Nitrogen-14 NQR Multiple-Pulse Spin-locking in the Axial Electric Field Gradient

1994 ◽  
Vol 49 (1-2) ◽  
pp. 97-102 ◽  
Author(s):  
G . B. Furman
Keyword(s):  
Electric Field ◽  
Floquet Theory ◽  
Electric Quadrupole ◽  
Dipole Interaction ◽  
Quasi Equilibrium ◽  
Multiple Pulse ◽  
Crystal Electric Field ◽  
Equilibrium Magnetization ◽  
Spin Locking ◽  
Pulse Radiofrequency

Abstract The behavior of a nuclear spin-1 system with the Hamiltonian including: a) the interaction of the electric quadrupole moment of nuclei with the axial gradient of the crystal electric field; b) a homonuclear and heteronuclear dipole-dipole coupling; and c) the interaction with a multiple pulse radiofrequency field of arbitrary orientation was considered. The effective Hamiltonian is con­structed by using the Floquet theory. The secular parts of the homonuclear and heteronuclear dipole-dipole interaction was found and the quasi-equilibrium magnetization was calculated.

Dipolar Order and Spin-Lattice Relaxation in a Liquid Entrapped into Nanosize Cavities

2011 ◽  
Vol 66 (12) ◽  
pp. 779-783 ◽  
Author(s):  
Gregory Furman ◽  
Shaul Goren
Keyword(s):  
Relaxation Time ◽  
Pulse Sequence ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Local Fields ◽  
Spin Lattice Relaxation ◽  
Quasi Equilibrium ◽  
Cavity Size ◽  
Spin Lattice ◽  
Dipolar Order

It was shown that by means of the two-pulse sequence, the spin system of a liquid entrapped into nanosize cavities can be prepared in quasi-equilibrium states of high dipolar order, which relax to thermal equilibrium with the molecular environment with a relaxation time T1d. Measurements of the inverse dipolar temperature and spin-lattice relaxation time in the local fields provide an important information about the cavity size V, its shape F, and orientation θ (with respect to the external magnetic field) of the nanopores.

scholarly journals A study of the relaxation parameters of a 13C-enriched methylene carbon and a 13C-enriched perdeuteromethylene carbon attached to chymotrypsin

1991 ◽  
Vol 280 (3) ◽  
pp. 649-657 ◽  
Author(s):  
J P G Malthouse ◽  
M D Finucane
Keyword(s):  
Enzyme Inhibitor ◽  
Pulse Sequence ◽  
Spin Echo ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Relaxation Parameters ◽  
Scalar Relaxation ◽  
Rotational Correlation ◽  
Field Strengths

L-1-Chloro-4-phenyl-3-tosylamido[1-13C]butan-2-one (Tos-[1-13C]Phe-CH2Cl) and Tos-[1-13C,2H2]Phe-CH2Cl were prepared and used to alkylate delta-chymotrypsin. The relaxation parameters of the 13C-n.m.r. signal resulting from the alkylation of histidine-57 in both enzyme-inhibitor complexes were determined at 1.88 T and 6.34 T as well as the spin-lattice relaxation times of the backbone alpha-carbon atoms of the unenriched Tos-Phe-CH2-delta-chymotrypsin complex. It is concluded that the species examined do not have significant internal librational motions and that the rotational correlation time of the monomeric enzyme-inhibitor complex is 16.0 +/- 3.2 ns. The signal from the 13C-enriched atom of Tos-[1-13C,2H2]Phe-CH2Cl is split into a quintet (JCD = 23 Hz) whereas in the Tos-[1-13C,2H2]Phe-CH2-delta-chymotrypsin complex the signal from the 13C-enriched inhibitor carbon atom is decoupled. This decoupled signal had linewidths of 16 +/- 3 Hz and 52 +/- 2 Hz at 1.88 T and 6.34 T respectively, whereas linewidths at 40 +/- 2 Hz and 53 +/- 4 Hz were obtained for the same signal in the Tos-[1-13C]Phe-CH2-delta-chymotrypsin complex at 1.88 T and 6.34 T respectively. Therefore whereas deuteration produces a 2.5-fold reduction in linewidth at 1.88 T there is no significant decrease in the linewidth at 6.34 T. This result is explained by using the rigid rotor model, which predicts that the quadrupolar spin-lattice relaxation rate will be faster at low field strengths, resulting in more efficient deuterium decoupling by scalar relaxation of the second kind at lower field strengths. It is also predicted that deuterium decoupling by scalar relaxation will become less efficient as rotational correlation times increase. The consequences of these predictions for the detection of 13C-enriched atomic probes of proteins are discussed. It is also shown that a spin-echo pulse sequence can be used to remove signals due to protonated carbon atoms without attenuating the signal due to deuterated carbon atoms.

Spin-Lattice Relaxation of Dipolar Energy in Fluid Confined to Nanosize Cavities

2012 ◽  
Vol 721 ◽  
pp. 47-52 ◽  
Author(s):  
Gregory Furman ◽  
Shaul Goren
Keyword(s):  
Experimental Data ◽  
Spin System ◽  
Thermal Equilibrium ◽  
Pulse Sequence ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Quasi Equilibrium ◽  
Bounded Region ◽  
Spin Lattice ◽  
Dipolar Order

We shown that by means of the two pulse sequence, the spin system of a liquid entrapped into nanosize cavities can be prepared in quasi-equilibrium states of high dipolar order. Then the dipolar order relaxes to thermal equilibrium with the lattice with a relaxation time T1d. It was shown that large number of spins T1d increases as the square to the concentration of the molecules C and decreases as inverse of the number of spins, T1d - C²/N. Study of spin lattice relaxation of dipolar energy in a spin system under the bounded region is important for extracting very useful parameter characterized nanomaterials from NMR experimental data.

Spin Diffusion in Pure Multiple-Pulse NQR

2000 ◽  
Vol 55 (1-2) ◽  
pp. 54-60 ◽  
Author(s):  
G. B. Furman ◽  
S. D. Goren ◽  
A. M. Panich ◽  
A. I. Shames
Keyword(s):  
Spin Diffusion ◽  
Diffusion Processes ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Effective Field ◽  
Spin Lattice Relaxation ◽  
Multiple Pulse ◽  
Spin Lattice ◽  
Paramagnetic Impurities ◽  
Spin Locking

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 obtained diffusion equation was obtained allows to find the time dependence of the magnetization in the effective field. The spin lattice relaxation times were calculated, both for direct and diffusion regimes, as functions of the correlation time and multiple-pulse parameters. Measurements of relaxation times in rotating frame allow to determine the diffusion coefficient and the radius of the diffusion barrier in γ-irradiated polycrystalline samples of NaCIO3.

T2-weighted spin-echo pulse sequence with variable repetition and echo times for reduction of MR image acquisition time.

Radiology ◽  
1991 ◽  
Vol 180 (2) ◽  
pp. 551-556 ◽  
Author(s):  
R K Butts ◽  
F Farzaneh ◽  
S J Riederer ◽  
J N Rydberg ◽  
R C Grimm
Keyword(s):  
Pulse Sequence ◽  
Spin Echo ◽  
Image Acquisition ◽  
Acquisition Time ◽  
Mr Image ◽  
Image Acquisition Time ◽  
Echo Pulse

Potentiodynamic examination of electrode kinetics for electroactive adsorbed species: applications to the reduction of noble metal surface oxides

1969 ◽  
Vol 310 (1503) ◽  
pp. 541-563 ◽  
Keyword(s):  
Noble Metals ◽  
Reaction Rate ◽  
Substrate Surface ◽  
Intrinsic Property ◽  
Surface Heterogeneity ◽  
Surface Oxide ◽  
Rate Equations ◽  
Quasi Equilibrium ◽  
Linear Potential ◽  
Reaction Velocity

The relation between reaction rate and potential (or time) for electrochemical surface processes occurring under potentiodynamic control (linear potential-time programme) has been investigated with particular reference to the behaviour of thin surface oxide films on noble metals. The kinetics of processes involving adsorbed electroactive species are treated for several model cases; the rate equations are developed for mechanisms involving various reaction orders or for processes involving adsorbed reactant interactions and surface heterogeneity effects. By examination of the dependence of the reaction rate (current) with time and the effect of potential scan rate, v , on the maximum reaction velocity and the potential at which it occurs, the models may be distinguished. In this manner, the inter­dependence of v and the reaction velocity constants k a and k c for the anodic oxidation and the cathodic reduction processes respectively, can be quantitatively established. The relation between quasi-equilibrium situations where the reverse reaction is significant and irreversible situations where it is not can be demonstrated. Heterogeneity terms introduced into the kinetic relations express deviations from Langmuir adsorption behaviour and may be an intrinsic property of the substrate surface or a property of the adsorbed reactant (induced heterogeneity). Applications of the treatment are made to reduction of surface oxide species at the noble metals and the significance of hysteresis and time effects in the processes of electrochemical formation and reduction of surface oxide at platinum, rhodium, iridium and palladium is investigated.

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