# Ultralow-field Nuclear Magnetic Resonance Asymmetric Spectroscopy

## TL;DR

This paper investigates the asymmetric spectral amplitudes observed in ultralow-field NMR, providing a comprehensive model, new experimental observations, and methods to eliminate asymmetry, revealing additional information from the spectra.

## Contribution

It introduces a comprehensive model explaining spectral asymmetry in ultralow-field NMR and demonstrates how to suppress it while extracting more information from the spectra.

## Key findings

- Developed a model explaining spectral asymmetry.
- Observed unprecedented asymmetric spectra.
- Proposed methods to eliminate spectral asymmetry.

## Abstract

Ultralow-field nuclear magnetic resonance (NMR) provides a new regime for many applications ranging from materials science to fundamental physics. However, the experimentally observed spectra show asymmetric amplitudes, differing greatly from those predicted by the standard theory. Its physical origin remains unclear, as well as how to suppress it. Here we provide a comprehensive model to explain the asymmetric spectral amplitudes, further observe more unprecedented asymmetric spectroscopy and find a way to eliminate it. Moreover, contrary to the traditional idea that asymmetric phenomena were considered as a nuisance, we show that more information can be gained from the asymmetric spectroscopy, e.g., the light shift of atomic vapors and the sign of Land$\acute{\textrm{e}}$ $g$ factor of NMR systems.