# Simultaneous observation of high order multiple quantum coherences at ultralow magnetic fields

## TL;DR

This paper introduces a method to simultaneously observe high-order heteronuclear quantum coherences at ultralow magnetic fields, enhancing NMR capabilities where chemical shifts are negligible.

## Contribution

The study demonstrates a novel approach combining SABRE, SQUID-based detection, and COSY to observe and analyze multiple quantum coherences at ultralow magnetic fields.

## Key findings

- Successful detection of up to third-order heteronuclear quantum coherences.
- Comparison shows COSY provides quantitative analysis of coherences.
- Method enhances ultralow field NMR spectroscopy capabilities.

## Abstract

We present a method for the simultaneous observation of heteronuclear multi-quantum coherences (up to the 3rd order), which give an additional degree of freedom for ultralow magnetic field (ULF) MR experiments, where the chemical shift is negligible. The nonequilibrium spin state is generated by Signal Amplification By Reversible Exchange (SABRE) and detected at ULF with SQUID-based NMR. We compare the results obtained by the heteronuclei Correlated SpectroscopY (COSY) with a Flip Angle FOurier Series (FAFOS) method. COSY allows a quantitative analysis of homo- and heteronuclei quantum coherences.

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Source: https://tomesphere.com/paper/1905.02485