Title page for ETD etd-08222013-090654
|Type of Document
||Byvik, Charles E.
||Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate
|Wollan, David S.
|Gilmer, Thomas E.
|Jacobs, James A.
|Tipsword, Ray F.
|Williams, Clayton D.
- metallic solids
- polarization of nuclei
- non-metallic solids
|Date of Defense
The dynamic nuclear polarization of hydrogen nuclei by the solid
effect in single crystals of samarium doped lanthanum magnesium nitrate
(Sm:LMN) has been studied theoretically and experimentally. The equations
of evolution governing the dynamic nuclear polarization by the
solid effect have been derived in detail using the spin temperature
theory and the complete expression for the steady-state enhancement of
the nuclear polarization has been calculated. For well-resolved solid
effect transitions at microwave frequencies ω ~ ωe ± ωn, the expression
for the steady-state enhancement differs from the expression obtained by
the rate equation approach by small terms which become zero at ω ~ ωe ± ωn Experimental enhancements of the proton polarization
were obtained for eight crystals at 9.2 GHz and liquid helium temperatures.
The samarium concentration ranged from 0.1 percent to 1.1 percent as determined by X-ray fluorescence. A peak enhancement of 181
was measured for a 1.1 percent Sm:LMN crystal at 3.0∘ K. The maximum
enhancements extrapolated with the theory using the experimental data
for peak enhancement versus microwave power and correcting for leakage,
agree with the ideal enhancement (24O in this experiment) within
experimental error for three of the crystals. The calculated satellite separation was within 6 percent of the measured separation for each of
the enhancement curves and the peak positive and negative enhancements
were equal for all but two of the crystals. The nuclear spin—lattice
relaxation time was measured for one of the crystals between l.6∘ K and
4.2∘ K. To account for nuclear spin—lattice relaxation, spin diffusion
theory in the rapid airrusion limit was incorporated into the results
of the spin temperature theory of the solid effect. The experimental
results indicate that the spin temperature theory is a quantitatively
correct approach for the description of dynamic nuclear polarization
by the solid effect for well—resolved solid effect transitions.
|| Approximate Download Time
| 28.8 Modem
|| 56K Modem
|| ISDN (64 Kb)
|| ISDN (128 Kb)
|| Higher-speed Access
If you have questions or technical
problems, please Contact DLA.