Nuclear spin conversion in H<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O

Cacciani, P.; Cosléou, J.; Khelkhal, M.

doi:10.1103/physreva.85.012521

Cited by 41 publications

(30 citation statements)

References 43 publications

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“…However, unlike other small polyatomic molecules exhibiting spin isomerism, such as fluoromethane or ethylene [15,16] , which were spin-isomerically enriched using the light induced drift technique [7] , this has not been achieved for water. Separation through selective adsorption on surfaces was reported [17] , but these results remain controversial and could not be reproduced [18][19][20][21] . Thus, studies of spin-conversion dynamics in water have been limited to water embedded in rare gas matrices, with relative spin populations modified by the sample temperature [22] .…”

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confidence: 99%

“…Separation through selective adsorption on surfaces was reported, [17] but these results remain controversial and could not be reproduced. [18][19][20][21] Thus, studies of spin-conversion dynamics in water have been limited to water embedded in rare gas matrices, with relative spin populations modified by the sample temperature. [22] A recent study investigated nuclear-spin conversion in the gas phase and found no spin conversion for water monomers.…”

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Separating Para and Ortho Water

et al. 2014

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Water exists as two nuclear-spin isomers, para and ortho, determined by the overall spin of its two hydrogen nuclei. For isolated water molecules the conversion between these isomers is forbidden and they act as different molecular species. Yet, these species are not readily separated and no pure para sample has been produced. Accordingly, little is known about their specific physical and chemical properties, conversion mechanisms, or interactions. Here, we demonstrate the production of isolated samples of both spin isomers in pure beams of para and ortho water in their respective absolute ground state. These single-quantum-state samples are ideal targets for unraveling spin-conversion mechanisms, for precision spectroscopy and fundamentalsymmetry-breaking studies, and for spin-enhanced applications, e. g., laboratory astrophysics and -chemistry or hypersensitized NMR experiments.Significant efforts have been undertaken to separate and study the nuclear-spin isomers of water, motivated by their importance in a wide variety of scientific disciplines. This ranges from the astronomical importance of the ortho-para ratio [1][2][3][4][5] , to studies of nuclear-spin conversion [6,7] , selection rules and reactive collisions [8][9][10] or symmetry breaking [11] . Spin-enriched samples furthermore would allow for hypersensitized NMR experiments via polarization transfer reactions [12][13][14] . However, unlike other small polyatomic molecules exhibiting spin isomerism, such as fluoromethane or ethylene [15,16] , which were spin-isomerically enriched using the light induced drift technique [7] , this has not been achieved for water. Separation through selective adsorption on surfaces was reported [17] , but these results remain controversial and could not be reproduced [18][19][20][21] . Thus, studies of spin-conversion dynamics in water have been limited to water embedded in rare gas matrices, with relative spin populations modified by the sample temperature [22] . A recent study investigated nuclear-spin conversion in the gas-phase and found no spin conversion for water monomers [23] .Recently, the production of a single spin isomer of water in a magnetic-hexapole-focuser setup was demonstrated [24] . One of the magnetically active spin projections (m = +1) of ground-state ortho water was magnetically focused into the interaction volume, while all other spin-projection states were defocused or diverged unaffected by the field. The purity of the produced ortho beam was later evaluated as 93 %, with simulations suggesting an upper limit for the achievable purity of 97 % [24,25] .Here, we experimentally demonstrate the production of pure samples of both, para and ortho water, the latter further separated into its M = 0 and M = 1 angular momentum projections, in the gas-phase. The produced single-quantum-states are ideally suited for further experiments on nuclear-spin conversion under collision-free conditions, nuclear-spin-dependent reactivity [8] , trapping of single spin-isomer samples in electromagnetic traps [26] ...

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Separating Para and Ortho Water

et al. 2014

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“…The electric dipole moments couple to the molecular angular momenta in the J = 1 states, which are in turn coupled to the nuclear spins through the spin-rotation mechanism-which is already known as a route to unimolecular spin conversion for water in high rotational states. 65,66 The mechanism postulated here would extend the spin-rotation mechanism to bimolecular processes in a low-temperature solid. The rapid increase in the spin conversion rates above 10 K (Table I) could be associated with an increased population of higher rotational levels, which have larger spin-rotation interactions.…”

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Nuclear spin conversion of water inside fullerene cages detected by low-temperature nuclear magnetic resonance

Mamone

Concistrè

Carignani

et al. 2014

The Journal of Chemical Physics

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Articles you may be interested in 194306 (2014) Nuclear spin conversion of water inside fullerene cages detected by low-temperature nuclear magnetic resonance The water-endofullerene H 2 O@C 60 provides a unique chemical system in which freely rotating water molecules are confined inside homogeneous and symmetrical carbon cages. The spin conversion between the ortho and para species of the endohedral H 2 O was studied in the solid phase by lowtemperature nuclear magnetic resonance. The experimental data are consistent with a second-order kinetics, indicating a bimolecular spin conversion process. Numerical simulations suggest the simultaneous presence of a spin diffusion process allowing neighbouring ortho and para molecules to exchange their angular momenta. Cross-polarization experiments found no evidence that the spin conversion of the endohedral H 2 O molecules is catalysed by 13 C nuclei present in the cages.

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“…B. Fluormethan oder Ethylen, [15,16] per lichtinduzierter Drift produziert werden konnten, [7] ist dies bisher für Wasser nicht gelungen. [18][19][20][21] Untersuchungen der Spinumwandlung in Wasser wurden daher nur an Molekülen in kalten Edelgasmatrices durchgeführt, wobei die relative Besetzung der Spinzustände durch die Probentemperatur kontrolliert werden kann. [18][19][20][21] Untersuchungen der Spinumwandlung in Wasser wurden daher nur an Molekülen in kalten Edelgasmatrices durchgeführt, wobei die relative Besetzung der Spinzustände durch die Probentemperatur kontrolliert werden kann.…”

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Trennung von para‐und ortho‐Wasser

et al. 2014

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Wasser existiert in Form zweier Kernspinisomere, para und ortho, definiert durch den Gesamtspin der zwei Wasserstoffatomkerne. In isolierten Wassermolekülen ist die Umwandlung zwischen den beiden Isomeren quantenmechanisch verboten, und sie kçnnen als zwei verschiedene Molekülspezies betrachtet werden. Ihre Trennung ist nicht trivial, und reine Proben von para-Wasser sind bisher nicht erzeugt worden. Daher sind die physikalischen und chemischen Eigenschaften, Umwandlungsmechanismen und Wechselwirkungen der beiden Isomere kaum bekannt. Hier demonstrieren wir die Isolierung beider Spinisomere in reinen Molekülstrahlen von para-und ortho-Wasser im jeweiligen absoluten Grundzustand. Die Moleküle in einzelnen Quantenzuständen sind ideale Proben für Studien zu Umwandlungsmechanismen der Isomere, für Präzisionsspektroskopie, zur Untersuchung fundamentaler physikalischer Symmetriebrechung sowie für kernspinbasierte Anwendungen, z. B. Laborexperimente zur Astrophysik und -chemie oder hochempfindliche NMR-Experimente.

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Nuclear spin conversion in H2O

Cited by 41 publications

References 43 publications

Separating Para and Ortho Water

Separating Para and Ortho Water

Nuclear spin conversion of water inside fullerene cages detected by low-temperature nuclear magnetic resonance

Trennung von para‐und ortho‐Wasser

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