Limbach, H. H. ; Buntkowsky, G. ; Mathes, J. ; Gründemann, S. ; Pery, T. ; Walaszek, B. ; Chaudret, B. (2006)
Novel insights into the mechanism of the ortho/para spin conversion of hydrogen pairs: Implications for catalysis and interstellar water.
In: Chemphyschem, 7 (3)
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
The phenomenon of exchange coupling is taken into account in the description of the magnetic nuclear spin conversion between bound ortho- and para-dihydrogen. This conversion occurs without bond breaking, in contrast to the chemical spin conversion. It is shown that the exchange coupling needs to be reduced so that the corresponding exchange barrier can increase and the given magnetic interaction can effectively induce a spin conversion. The implications for related molecules such as water are discussed. For ice, a dipolar magnetic conversion and for liquid water a chemical conversion are predicted to occur within the millisecond timescale. It follows that a separation of water into its spin isomers, as proposed by Tikhonov and Volkov (Science 2002, 296, 2363), is not feasible. Nuclear spin temperatures of water vapor in comets, which are smaller than the gas-phase equilibrium temperatures, are proposed to be diagnostic for the temperature of the ice or the dust surface from which the water was released.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2006 |
| Autor(en): | Limbach, H. H. ; Buntkowsky, G. ; Mathes, J. ; Gründemann, S. ; Pery, T. ; Walaszek, B. ; Chaudret, B. |
| Art des Eintrags: | Bibliographie |
| Titel: | Novel insights into the mechanism of the ortho/para spin conversion of hydrogen pairs: Implications for catalysis and interstellar water |
| Sprache: | Englisch |
| Publikationsjahr: | 2006 |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Chemphyschem |
| Jahrgang/Volume einer Zeitschrift: | 7 |
| (Heft-)Nummer: | 3 |
| URL / URN: | http://apps.webofknowledge.com/full_record.do?product=WOS&se... |
| Kurzbeschreibung (Abstract): | The phenomenon of exchange coupling is taken into account in the description of the magnetic nuclear spin conversion between bound ortho- and para-dihydrogen. This conversion occurs without bond breaking, in contrast to the chemical spin conversion. It is shown that the exchange coupling needs to be reduced so that the corresponding exchange barrier can increase and the given magnetic interaction can effectively induce a spin conversion. The implications for related molecules such as water are discussed. For ice, a dipolar magnetic conversion and for liquid water a chemical conversion are predicted to occur within the millisecond timescale. It follows that a separation of water into its spin isomers, as proposed by Tikhonov and Volkov (Science 2002, 296, 2363), is not feasible. Nuclear spin temperatures of water vapor in comets, which are smaller than the gas-phase equilibrium temperatures, are proposed to be diagnostic for the temperature of the ice or the dust surface from which the water was released. |
| Freie Schlagworte: | exchange coupling hydrogen interstellar chemistry spin conversion water chemistry induced polarization magnetic-resonance molecular-hydrogen h-2 nmr complexes exchange proton |
| Zusätzliche Informationen: | 025XL Times Cited:42 Cited References Count:27 |
| Fachbereich(e)/-gebiet(e): | 07 Fachbereich Chemie 07 Fachbereich Chemie > Eduard Zintl-Institut > Fachgebiet Physikalische Chemie |
| Hinterlegungsdatum: | 27 Okt 2014 20:44 |
| Letzte Änderung: | 29 Mai 2019 10:02 |
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