Characterization of RF Inhomogeneity via NOON states

TL;DR

This paper introduces a novel method using NOON states for rapid, high-power RF inhomogeneity characterization in NMR, providing detailed inhomogeneity and correlation profiles with improved efficiency.

Contribution

The work presents a new NOON state-based technique for quantitative RF inhomogeneity measurement, including a model for inhomogeneity profiles and extension to multi-channel correlation analysis.

Findings

NOON states enable faster decay of Torrey oscillations, allowing shorter pulse durations.

The method accurately characterizes RF inhomogeneity profiles in high-resolution NMR probes.

Extension to two-channel correlation profiling provides comprehensive inhomogeneity mapping.

Abstract

We describe a method for quantitative characterization of radio-frequency (RF) inhomogeneity using NOON states. NOON states are special multiple-quantum coherences which can be easily prepared in star-topology spin-systems. In this method we exploit the high sensitivity of the NOON states for z-rotations. As a result, Torrey oscillations with NOON states decay much faster than that of single quantum coherences. Therefore the present method requires shorter pulse durations, and enables the study of inhomogeneity at higher RF powers. To model such a inhomogeneity profile, we propose a two-parameter asymmetric Lorentzian function. The experiments are carried out in 1H channels of two different high-resolution NMR probes and the results are compared. Finally, we also extend the NOON state method to characterize the inhomogeneity correlations between two RF channels. We obtain the correlation profile between 1H and 31P channels of an NMR probe by constructing a five-parameter asymmetric-3D Lorentzian model.