### SPIN-LATTICE RELAXATION TIME FOR I$sup 127$ IN KI IN THE TEMPERATURE RANGE 2 K TO 20 KSPIN-LATTICE RELAXATION TIME FOR I$sup 127$ IN KI IN THE TEMPERATURE RANGE 2 K TO 20 K

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 Author Briscoe, C. V. ♦ Squire, C. F. Source United States Department of Energy Office of Scientific and Technical Information Content type Text Language English
 Subject Keyword PHYSICS AND MATHEMATICS ♦ CRYSTALS ♦ DIFFUSION LENGTH ♦ ELECTRIC FIELDS ♦ ELECTRIC MOMENTS ♦ ENERGY LEVELS ♦ ERRORS ♦ HELIUM ♦ HYDROGEN ♦ INTERACTIONS ♦ IODINE 127 ♦ LATTICES ♦ LIQUIDS ♦ LOW TEMPERATURE ♦ MAGNETIC FIELDS ♦ MEASURED VALUES ♦ NUCLEAR MAGNETIC RESONANCE ♦ NUCLEAR THEORY ♦ POTASSIUM IODIDES ♦ POWDERS ♦ RELAXATION ♦ SLOWDOWN ♦ SPECTROMETERS ♦ SPIN ♦ WIDTH Abstract The spin-lattice relaxation time, T/sub 1/, for I/sup 127/ in both single crystal and powdered KI was measured in the temperature range 2 to 20 deg K using a Pound-Watkins type nuclear magnetic resonance spectrometer. In the liquid hydrogen temperature range T/sub 1/ is approximately the same for both the single crystal and the powder specimens, varying from 20 sec at 20 deg K to 70 sec at 14 deg K. Both the temperature dependence and the magnitude of T/sub 1/ in this temperature range can be explained on the basis of a theory of nuclear quadrupolar spin-latice relaxation proposed by Van Kranendonk. In the liquid helium temperature range (2 to 4 deg K). T/sub 1/ is constant within experimental error. For the single crystal T/sub 1/ = 6.9 x 10/sup 3/ sec and for the powder specimen T/sub 1/ = 6.0 x 10/sup 2/ sec in this temperature range. These values of T/sub 1/ are less by orders of magnitude than is predicted using Van Kranendonk's theory. The I/sup 127/ resonance (spin I = 5/2 in units of h(line across) consisted of a narrow (less than 1 guass halfwidth) central line with broad (>15 gauss) weak wings. This is attributed, according to Pound, to a shift in the nuclear magnetic energy levels brought about by the interaction of the nuclear quadrupole moment with electric field gradients present in the specimens. (auth) partial adiabatic demagnetization and adiabatic rotation. The area under the nuclear resonance was used as a thermometric parameter. The area did not obey Curie's law as a result of the temperature-dependent local rf field. A T-T relation was derived which gave temperature ratios on adiabatic rotation which agreed within 5- 10% with ratios calculated from the properties of the crystal. The lowest measured temperature was 5 x 10/sup -3/ deg K. A study of the structure of the resonance showed that the splittings were caused by the average magnetization of ihe cerium ions and that the protons were at least 5 A from the cerium ions. (auth) ISSN 0031899X Educational Use Research Learning Resource Type Article Publisher Date 1958-12-01 Publisher Department Rice Inst., Houston, Texas Journal Physical Review Volume Number 112 Organization Rice Inst., Houston, Texas