Interaction of muonium with oxygen on silica powder surfaces |
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| Authors: | J R Kempton R F Marzke D G Fleming A C Gonzalez S K Leung J J Pan P W Percival M Senba A Tempelmann |
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| Institution: | (1) TRIUMF and Department of Chemistry, University of British Columbia, 4004 Wesbrook Mall, V6T 2A3 Vancouver, B.C., Canada;(2) Department of Physics, Arizona State University, 85287 Tempe, AZ, U.S.A.;(3) TRIUMF and Department of Chemistry, Simon Fraser University, V5A 1S6 Burnaby, B.C., Canada |
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| Abstract: | Results of the first μSR studies using Merck FO Optipur silica powder, which contains paramagnetic impurities at the ppb level
and has a surface area of 610±20 m2/g. are reported. Above 20 K, the transverse field muonium relaxation rate is roughly constant at 0.5 μs−1. Upon the addition of oxygen at ppm levels, the relaxation rate increases linearly with O2 concentration in the temperature range from 40–100 K yielding two-dimensional depolarization rate constants on the order
of 10−4 cm2 molecule−1 s−1. As the temperature is increased further, both oxygen and muonium desorb from the surface yielding a three-dimensional rate
constants at 300 K of 3.1(3)×10–10−10 cm3 molecule−1 s−1, in agreement with the gas phase value. Longitudinal field measurements suggest that MuO2 is formed and is able to spin exchange with other oxygen molecules. |
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