Nicholas N. Kuzma1, Huseyin Kara, 12, Mehrdad Pourfathi1, Philip Manasseh3, Jan H. Ardenkjr-Larsen4, Stephen J. Kadlecek1, Rahim R. Rizi1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States; 2Astronomy and Physics, University of Pennsylvania, Philadelphia, PA, United States; 3Department of Chemistry, Earlham College, Richmond, IN, United States; 4GE Healthcare, Brndby, Denmark
At 1.5K and 5T, 129Xe NMR spectra of a homogeneous xenon/1-propanol/trityl-radical mixture exhibit a single 1H-broadened peak. Another peak appears upon 4-hour annealing at 125K. Its characteristic width and chemical shift indicate spontaneous formation of pure Xe clusters. Microwave irradiation can bring both peaks to either positive or negative polarization. Time evolution of DNP in pure Xe clusters can be understood in terms of spin diffusion and T1 relaxation. Our data can be used 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.