Effects of Finite Gradient-Pulse Widths in Pulsed-Field-Gradient Diffusion Measurements

Mitra, P. P., Halperin, B. I. (1995) Effects of Finite Gradient-Pulse Widths in Pulsed-Field-Gradient Diffusion Measurements. Journal of Magnetic Resonance, Series A, 113 (1). pp. 94-101. ISSN 10641858 (ISSN)

URL: http://www.sciencedirect.com/science/article/pii/S...
DOI: 10.1006/jmra.1995.1060

Abstract

The effects of finite gradient-pulse widths on NMR diffusion measurements for fluids in restricting geometries are studied. It is shown that the echo amplitude is the spatial Fourier transform of a "center-of-mass" propagator, which reduces to the usual diffusion propagator in the limit of zero pulse widths. A finite gradient-pulse width δ effectively changes the pore shape, making isolated pores appear smaller than their actual size. The diffraction analogy still holds for long diffusion times, with the fluid density ρ(r) being replaced by pcm(r, δ). This quantity, the "center-of-mass distribution function," is the spatial probability distribution of the center of mass of Brownian trajectories of duration δ in the pore space. For a periodic pore space, "Bragg" peaks still appear in the amplitude at the reciprocal lattice vectors. The heights of these peaks are enhanced for small δ but reduced for δ. A number of results valid for small δ and piecewise smooth pore surfaces are presented. © 1995 Academic Press. All rights reserved.

Item Type: Paper
Subjects: physics > fluid dynamics
Investigative techniques and equipment > magnetic resonance imaging
physics
CSHL Authors:
Communities: CSHL labs > Mitra lab
Depositing User: CSHL Librarian
Date: 1995
Date Deposited: 02 Apr 2012 20:08
Last Modified: 10 Feb 2017 20:03
URI: http://repository.cshl.edu/id/eprint/25855

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