Deuteron spin lattice relaxation in benzene, bromobenzene, water and ammonia

Abstract

The deuteron spin-lattice relaxation times, T _1Q, have been measured for benzene, water and ammonia from the melting point to the liquid-vapour critical temperature and for bromobenzene over a smaller temperature range. The results are compared with previously measured proton spin-lattice relaxation times. It is shown that the deuteron T _1Q values agree with the proton intramolecular T ₁ values for benzene, thus confirming the separation of the dipolar and spin-rotation contributions performed by Powles and Figgins [1]. A value of the electric quadrupole coupling constant, e ² qQ/th, is deduced, which agrees with the value for the molecule in the solid. For bromobenzene a value of e ² qQ/h=175±10 khz is obtained in a similar way. For water and ammonia a solution is found to the classic N.M.R. problem of separating the inter and intra-dipolar interaction contributions to the dipolar relaxation rate. The two contributions are about equal, in agreement with theory. The separation of the spin-rotation contribution performed by Smith and Powles [2] is confirmed. A value of e ² qQ/th of 230 ± 10 khz is obtained for water molecules in liquid water, which is the value found by quadrupole splitting of the deuteron resonance in ice rather than the value, 318·6 khz, for the molecule in the gas phase. This is taken to indicate that the molecules in liquid water are strongly hydrogen bonded even at high temperatures. The results for ammonia are similar to those for water, the deduced e ² qQ/h value is also well below that for the free molecule.