Nonlinear NMR dynamics in hyperpolarized liquid 3He

TL;DR

This paper investigates nonlinear and nonlocal dipolar interactions in highly polarized liquid 3He, revealing instabilities in NMR evolution and demonstrating that the magic sandwich pulse sequence can significantly extend magnetization lifetime.

Contribution

It introduces the use of the magic sandwich pulse sequence to control nonlinear NMR instabilities in hyperpolarized liquid 3He, enhancing magnetization stability.

Findings

Magic sandwich sequence extends transverse magnetization lifetime by up to three orders of magnitude.

Dipolar interactions cause nonlinear instabilities in high polarization NMR.

Experimental and numerical analysis of NMR evolution under magic sandwich sequences.

Abstract

In a highly polarized liquid (laser-polarized 3He-4He mixtures in our experiment), dipolar magnetic interactions within the liquid introduce a significant nonlinear and nonlocal contribution to the Bloch equation that leads to instabilities during NMR evolution. We have launched a study of these instabilities using spin echo techniques. At high magnetizations, a simple 180 degree rf pulse fails to refocus magnetization, so we use a standard solid-state NMR pulse sequence: the magic sandwich. We report an experimental and numerical investigation of the effect of this sequence on unstable NMR evolution. Using a series of repeated magic sandwich sequences, the transverse magnetization lifetime can be increased by up to three orders of magnitude.