| Popis: |
We report direct measurements of nuclear spin‐lattice relaxation times (T1n) for the sodium anion, Na−, in solutions containing both sodium and a heavier alkali metal in 1,4,7,10‐tetraoxacyclododecane (12‐crown‐4, 12C4). Nuclear spin‐lattice relaxation in Na− is found to be essentially independent of the alkali counterion and to depend only weakly upon the concentration of sodide ion in solution. The temperature dependence of T1n for Na− was used to determine an activation energy for the processes responsible for spin relaxation. The results are consistent with a dominant, but very inefficient, quadrupolar relaxation mechanism which involves the modulation of the electric field gradient at Na− via the reorientation and/or translational motion of surrounding 12C4 molecules in the liquid. Furthermore, we find that solvation of Na− in 12C4 as well described by a model in which there is neither preferential orientation of 12C4 molecules nor a clearly identifiable first solvation shell around the sodide ion. C... |
