Paramagnetic relaxation of spin polarized 3He at coated glass walls |
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Authors: | A Deninger W Heil E W Otten M Wolf R K Kremer A Simon |
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Institution: | 1. Institut für Physik, 55099, Mainz, Germany 2. Max-Planck-Institut für Festk?rperforschung, 70569, Stuttgart, Germany
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Abstract: | In this second in a series of three papers on wall relaxation of
3He-spins we discuss relaxation in metal-coated glass cells in terms of
hyperfine coupling to paramagnetic conduction electrons at the Fermi
surface. This scales with the square of the work function of the coating and
thereby also with its He-adsorption energy. In this sense we investigate
coatings with particularly low work function and adsorption energy, namely
Cs and Cs-suboxides. Although we observe a suppression of relaxation rates
by two orders of magnitude as compared to bare Pyrex and fused silica walls,
their temperature dependence still shows the same Arrhenius dependence as
observed for bare substrates, instead of a T 3/2 dependence expected for
a metallic surface. From this finding we conclude that, on one hand, the
surface coverage is not complete and, on the other hand, the relaxation at
the alkali surface itself is extremely slow. This finding is supported, too,
by a semi-empirical estimate based on measured relaxation rates at ordinary
metal surfaces, rescaled then with the respective dependence on adsorption
energy. |
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