Separating molecular spin isomers is a challanging task, with potential applications in various fields ranging from astrochemistry to magnetic resonance imaging. A new promissing method for spin-isomer separation is magnetic focusing, a method which was shown to be capable of producing a molecular beam of ortho-water. Here, we present results from a modified magnetic focusing apparatus and show that it can be used to separate the spin isomers of acetylene and methane. From the measured focused profiles of the molecular beams and a numerical simulation analysis we provide estimations for the spin purity and the significantly improved molecular flux obtained with the new setup. Finally, we discuss the spin-relaxation conditions which will be needed to apply this new source for measuring NMR signals of single surface layer.
The mechanism for interconversion between the nuclear spin isomers (NSI) of HO remains shrouded in uncertainties. The temperature dependence displayed by NSI interconversion rates for HO isolated in an argon matrix provides evidence that confinement effects are responsible for the dramatic increase in their kinetics with respect to the gas phase, providing new pathways for o-HO↔p-HO conversion in endohedral compounds. This reveals intramolecular aspects of the interconversion mechanism which may improve methodologies for the separation and storage of NSI en route to applications ranging from magnetic resonance spectroscopy and imaging to interpretations of spin temperatures in the interstellar medium.
Magnetic focusing of a molecular beam formed from a rotationally-cooled supersonic jet of H 2 O seeded in argon is shown to yield water vapour highly enriched in the ortho-H 2 O nuclear spin isomer (NSI). Rotationally-resolved resonance-enhanced multi-photon ionisation time-of-flight mass spectrometry demonstrates this methodology enables the preparation of a beam of water molecules enriched to >98 % in the ortho-H 2 O NSI, that is having an ortho-to-para ratio (OPR) in excess of 50:1. The flux and quantum-state purity achieved through the methodology described herein could enable heterogeneous chemistry applications including the preparation of a nuclear spin-polarized water adlayers, making nuclear magnetic resonance investigations amenable to surface science studies, as well as laboratory investigations of NSI interconversion mechanisms and rates in ice and at its surface.
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