Relaxation dynamics of an unlike spin pair system

TL;DR

This study uses the Redfield master equation to analyze the relaxation dynamics of heteronuclear spin pairs with dipole-dipole interactions, providing detailed density matrix solutions and addressing previous discrepancies in longitudinal magnetization predictions.

Contribution

It offers new analytical expressions for density matrix elements and relaxation rates in heteronuclear spin systems, improving understanding of their relaxation behavior.

Findings

Multi-exponential evolution of magnetization confirmed

Predictions align with previous magnetization studies

Solutions resolve prior disagreements in longitudinal magnetization dynamics

Abstract

Redfield master equation was applied to study the dynamics of an ensemble of interacting pairs of unlike spins at room temperature. This spin quantum system is a workbench quantum model to analyze the relaxation dynamics of a heteronuclear two-level spin system interacting by a pure dipole-dipole coupling. Expressions for the density matrix elements and their relaxation rate constants of each coherence order were computed. In addition, the solutions were evaluated considering three initial quantum states, and the theoretical predictions, such as multi-exponential evolutions and enhancement, are behaviors that the solutions preserve and agree with previous studies performed for magnetization time evolutions. Moreover, the solutions computed to predict the dynamics of the longitudinal magnetization avoid the disagreement reported by I. Solomon.