Intermolecular Dipole–Dipole Relaxation of Xe Dissolved in Water |
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Authors: | Ivan E Dimitrov Ravinder Reddy John S Leigh |
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Institution: | a Department of Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, 19104;b Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104 |
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Abstract: | Intermolecular 129Xe–1H nuclear Overhauser effects and 129Xe longitudinal relaxation time measurements were used to demonstrate that the dipole–dipole coupling is the dominant relaxation mechanism for 129Xe in water, at room temperature. 129Xe–1H cross-relaxation rates were derived to be ςXeH 3.2 ± 0.3 × 10−3 s−1, independent of xenon pressure (in the range of 1–10 bar) and of the presence of oxygen. Corresponding xenon–proton internuclear distances were calculated to be 2.69 ± 0.12 Å. Using the magnitude of the dipole–dipole coupling and the spin density ratio between dissolved xenon and bulk water, it is estimated that 129Xe–1H spin polarization-induced nuclear Overhauser effects would yield little net proton signal enhancement in water. |
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Keywords: | xenon water dipole– dipole coupling NOE NMR |
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