Knight Shift and Nuclear Relaxation Times in Liquid Gallium

摘要

The Knight Shift in pure liquid gallium is measured as a function of temperature between 300 and 740K and obeys the empirical relation for change with temperature, Delta K = -(2.95 = 0.15) x 10 to the minus 7th power (T - 300). The shift varies only slightly with volume according to the expression K(V) = 0.00449 (V/V sub 0) to the minus 0.1 = 0.1 power at pressures between 1 and 5000 kg/cm. The pressure results disagree with the free electron model, and the intrinsic temperature dependence of K, coupled with the theory of Benedek and Kushida, suggests that the s-electron probability density at the nucleus, P sub F, decreases with negative curvature as a function of volume. The nuclear spin-lattice relaxation time, T sub 1, and spin-spin relaxation time, T sub 2, are measured from 270 to 470K. T sub 1 = T sub 2 at 298K to within 5%. The first results are in good agreement with the theory of Korringa for magnetic relaxation by electrons, when the theory is modified for correlation and exchange as described by Pines. The results are thought to be consistent with a bonded pair or group model of the liquid, whose lifetime is 10 to the minus 13th power sec or less.