Dynamic proton polarization in some rare earth ethyl sulphates
Wollan, David Strand
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https://hdl.handle.net/2142/25080
Description
Title
Dynamic proton polarization in some rare earth ethyl sulphates
Author(s)
Wollan, David Strand
Issue Date
1966
Doctoral Committee Chair(s)
Stapleton, H.J.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
dynamic polarization of protons
solid state effect
liquid helium
rare earth ethyl sulphates
Language
en
Abstract
"Measurements of the dynamic polarization of protons by the solid
state effect (""ef£et solide"") have been made at liquid helium temperatures
on single crystals of erbium-doped and neodymium-doped yttrium ethyl
sulphate ( (Er, Y)ES and (Nd, Y)ES). T he dynamic polarization was
induced by saturating the forbidden, satellite electron spin resonance
(ESR) line of the paramagnetic ion, and was measured by comparing
proton nuclear magnetic resonance (NMR) signals. Becau.se of its
higher hydrogen density, it was hoped that YES might be a better material
than the commonly-used lanthanum magnesium nitrate (LaMN) for use as
a polarized proton target for nuclear scattering experiments. Preliminary
results on (Er, Y)ES at 9.5 Gc/sec showed several features that prohibit
high proton polarizations. An anomalous behavior was observed in
o 167
(Er, Y)E,:S at 2.0 K du~ to the overlap of one of the Er hyperfine lines
with the main ESR transition, Preliminary experiments on (Nd, Y)ES at
9.5 Gc / sec indicated that this system was favorable for high polarizations.
o
Measqrements on (Nd, Y)ES at 69.5 Gc/sec, 16,200 Oe and 2.1 K gave a
maximum proton polarization of 0.215, as compared with the ideal
polarization of 0.66 expected under these conditions. The measured
polarizations in this latter case were concentration independent for
paramagnetic dopings from 0.25% to 2%. These results are in disagreement
with Jeffries' ""shell-of-influence"" model and Borghini's density
matrix theory of the solid state effect. Over 90% of the YES crystals
o .
cracked when cooled to 4.2 K. Because of thls and the low proton
polarizations attained, (Nd, Y)ES is not recommended as a polarized
proton target material for nuclear scattering experiments. Nonexponential
proton NMR relaxation decays were observed in (Nd, Y)ES
at 16,200 Oe and liquid helium temperatures."
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