Atomic Hydrogen in Thick H2 Films at Temperatures 0.05–2 K
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We describe experiments on hydrogen atoms stabilized in a 100 μm thick H2 film at temperatures between 0.05 and 2 K. The molecular hydrogen matrix was condensed directly from natural hydrogen gas. The H atoms are produced with a plasma discharge at temperatures below 1 K and studied with electron spin resonance. H densities of 2×1019 cm−3 in solid H2 were reached. As observed earlier in thin H2 films, we found a high stability of atomic populations and strong deviation from Boltzmann statistics of lowest two hyperfine states at the lowest temperatures. In thick films we found that the ESR resonance lines consisted of two closely spaced components with different widths indicating separate regions of high and low concentrations of H atoms in the H2 matrix. Upon warming, the two components show very different rates of recombination with the higher density component having a faster recombination rate at T>1 K. We discuss the atomic interactions and mobility, and also the structure of the samples of H atoms in the H2 matrix.
KeywordsHydrogen Quantum solid Electron-spin resonance
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