Para‐hydrogen enrichment and hyperpolarization

Abstract

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 radio‐frequency pulses is also considered. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 321–330, 2006