Decoupling of Spin Decoherence Paths near Zero Magnetic Field

TL;DR

This paper introduces a method to analyze and control nuclear spin decoherence mechanisms at zero and ultralow magnetic fields, enhancing magnetic resonance techniques and biomedical applications.

Contribution

It presents a novel approach to quantify and manipulate spin decoherence pathways using pulsed magnetic fields to switch between coupled and decoupled regimes.

Findings

Scalar relaxation due to deuterium limits spin lifetimes.

Pulsed magnetic fields can effectively decouple or couple nuclear spins.

Method broadens applications of hyperpolarized contrast agents.

Abstract

We demonstrate a method to quantify and manipulate nuclear spin decoherence mechanisms that are active in zero to ultralow magnetic fields. These include: (i) non-adiabatic switching of spin quantization axis, due to residual background fields; (ii) scalar pathways due to through-bond couplings between $^1$H and heteronuclear spin species, such as $^2$H used partially as an isotopic substitute for $^1$H. Under conditions of free evolution, scalar relaxation due to $^2$H can significantly limit nuclear spin polarization lifetimes and thus the scope of magnetic resonance procedures near zero field. It is shown that robust trains of pulsed dc magnetic fields that apply $\pi$ flip angles to one or multiple spin species may switch effective symmetry of the nuclear spin Hamiltonian, imposing decoupled or coupled dynamic regimes on demand. The method should broaden the spectrum of hyperpolarized biomedical contrast-agent compounds and hyperpolarization procedures that are used near zero field.