NMR Time Reversal Experiments in Highly Polarised Liquid 3He-4He Mixtures

TL;DR

This paper explores the use of a multi-echo NMR sequence to stabilize and analyze highly magnetized liquid helium mixtures, enabling improved measurements of spin diffusion under strong magnetic interactions.

Contribution

It demonstrates the application of a magic sandwich pulse sequence to stabilize magnetization and facilitate spin diffusion measurements in highly polarized liquid helium mixtures.

Findings

Successful stabilization of magnetization against dipolar interactions.

Potential for high-density spin diffusion measurements.

Evidence of non-linear, non-local magnetic effects in the system.

Abstract

Long-range magnetic interactions in highly magnetised liquids (laser-polarised 3He-4He dilute mixtures at 1 K in our experiment) introduce a significant non-linear and non-local contribution to the evolution of nuclear magnetisation that leads to instabilities during free precession. We recently demonstrated that a multi-echo NMR sequence, based on the magic sandwich pulse scheme developed for solid-state NMR, can be used to stabilise the magnetisation against the effect of distant dipolar fields. Here, we report investigations of echo attenuation in an applied field gradient that show the potential of this NMR sequence for spin diffusion measurements at high magnetisation densities.