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Detection of J-Coupling Using Atomic Magnetometer

Patent Number: 9,140,657


An embodiment of a method of detecting a J-coupling includes providing a polarized analyte adjacent to a vapor cell of an atomic magnetometer; and measuring one or more J-coupling parameters using the atomic magnetometer. According to an embodiment, measuring the one or more J-coupling parameters includes detecting a magnetic field created by the polarized analyte as the magnetic field evolves under a J-coupling interaction.

New Enabling Technology

Diagram shows ethanol, shields, vapor cell, reservoir, heater.
Implementation of low-field NMR molecular identification system. A chemical flows through a polarizing magnet (green) and into a magnetically shielded reservoir (blue) situated next to a chip-scale atomic magnetometer (gray). Magnetic measurements of NMR spectra taken after a short field pulse allow identification of molecules by their spectra.
Credit: NIST

Nuclear magnetic resonance (NMR) endures as one of the most powerful analytical tools for detecting chemical species and elucidating molecular structure. Zero-to-ultralow-field NMR (ZULF NMR) spectroscopy has emerged as a new, potentially portable and cost-effective modality to determine the molecular structure and properties of microfluidic chemical samples, using chemical signatures known as J-couplings or scalar coupling that reveal properties of the chemical bonds in samples. 

Conventional NMR spectrometers are large and utilize superconducting magnets operating at liquid helium temperatures to polarize the sample and generate large nuclear precession frequencies for inductive detection. This precludes their use in many situations where NMR would be beneficial. Benchtop NMR spectrometers are currently available operating in the 60 MHz range, but they often lack the desired sensitivity. 

No cryogens, compact dimensions

Detection of nuclear spins at low magnetic field requires magnetic sensors that have sensitivity at DC, unlike inductive pickup coils. Atomic magnetometers fit this purpose well. However, chemical shifts, which are typically used to identify molecular structure, cannot be measured at low fields. 

However, coupling between nuclear spins in a heteronuclear molecule (J-coupling) does remain at low fields and can be used to identify chemical species. The NIST-patented detector can resolve J-coupling resonances in fluids at low field enabling chemical species identification without the need for large cryogenically cooled magnets. It can be implemented on a single chip at low manufacturing cost.  

Tens of µT sensitivity.


  • Atomic magnetometer allows for detection of nuclear polarization at zero or low magnetic field
  • 1 kHz magnetometer bandwidth allows for resolution of J-coupling resonances between 13C and protons in simple hydrocarbons
  • Coupling to other nuclei such as 15N possible
Heteronuclear ethanol molecule with one 13C atom. The 13C nucleus interacts with the 1H nuclei at low magnetic field to produce NMR signals in the 100 Hz range unique to the molecular structure. These spectra allow identification of molecules with high specificity. 



  • Pharmaceutical drug discovery and design
  • Biomedical research
  • Catalyst evaluation and optimization
  • Liquid explosive detection
  • Manufacture of portable NMR detectors
  • Chemical production
  • Security monitoring


Potential partners include instrument manufacturers of NMR detectors used in the pharmaceutical and biomedical industries as well as national defense and homeland security programs. The NIST device can be widely applied in industry whenever trace amounts of chemical are being analyzed. For example, the pharmaceutical industry could use large arrays of these devices to perform parallel assays of a set of new trial drugs.

Created April 7, 2020, Updated February 11, 2021