This article begins with general considerations about enrichment of hydrogen gas into its para isomer (corresponding to nuclear spins in the singlet state); this is a necessary condition to obtain hyperpolarization from transfer of the relevant population excess. This transfer is generally mediated by a hydrogenation reaction such that the two protons become nonequivalent. The energy level populations of this new spin system can be calculated unambiguously using a density matrix formalism. This formalism is reviewed, and the authors propose a simple method that leads to the spin state after the hydrogenation reaction and the insertion of the sample in the NMR magnet. The effect of radiofrequency pulses is also considered.
Para-hydrogen enrichment and hyperpolarization
AIME, Silvio;GOBETTO, Roberto;REINERI, Francesca
2006-01-01
Abstract
This article begins with general considerations about enrichment of hydrogen gas into its para isomer (corresponding to nuclear spins in the singlet state); this is a necessary condition to obtain hyperpolarization from transfer of the relevant population excess. This transfer is generally mediated by a hydrogenation reaction such that the two protons become nonequivalent. The energy level populations of this new spin system can be calculated unambiguously using a density matrix formalism. This formalism is reviewed, and the authors propose a simple method that leads to the spin state after the hydrogenation reaction and the insertion of the sample in the NMR magnet. The effect of radiofrequency pulses is also considered.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.