Related Experiment Video
Updated: May 18, 2026

Hyperpolarized Xenon for NMR and MRI Applications
Published on: September 6, 2012
Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures
N N Kuzma1, M Pourfathi, H Kara
1Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. kuzma@upenn.edu
Abstract:
During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, (129)Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by (1)H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of (129)Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T(1) relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of (129)Xe polarization, from 5.3% to 21%.
Related Concept Videos
Nuclear Stability
To hold positively charged protons together in the...
Atomic Nuclei: Nuclear Spin State Population Distribution
Atomic Nuclei: Nuclear Relaxation Processes
VSEPR Theory and the Effect of Lone Pairs
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Noble Gases
The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name “noble” because they were assumed to be nonreactive since they have filled valence shells. In 1962, Dr. Neil Bartlett at the University of British Columbia proved this assumption to be false.

