Spin-lattice NMR relaxation by anomalous translational diffusion

TL;DR

This paper develops a theoretical model based on fractional diffusion equations to describe spin-lattice relaxation in inhomogeneous systems, validated by experiments on porous glass showing nonmonotonic relaxation behavior.

Contribution

It introduces a novel fractional diffusion-based framework for understanding spin-lattice relaxation in inhomogeneous media, aligning theory with experimental data.

Findings

Relaxation time depends on pore size in porous glass.

The relaxation rate exhibits a maximum at certain inhomogeneity levels.

The theoretical model accurately predicts experimental observations.

Abstract

A model-free theoretical framework for a phenomenological description of spin-lattice relaxation by anomalous translational diffusion in inhomogeneous systems based on the fractional diffusion equation is developed. The dependence of the spin-lattice relaxation time on the size of the pores in porous glass Vycor is experimentally obtained and found to agree well with our theoretical predictions. We obtain nonmonotonic behavior of the translational spin-lattice relaxation rate constant (it passes through a maximum) with the variation of the parameter referring to the extent of inhomogeneity of the system.