The nuclear spin–lattice relaxation time of 3He gas in contact with metallic and glass surfaces has been measured. The relaxation time of the gas in the presence of a glass surface is strongly dependent on both the permeability of the glass to helium and the concentration of paramagnetic impurities in the glass. Two relaxation mechanisms may in this case be distinguished, relaxation due to the diffusion of the gas into the glass and relaxation induced during the adsorption of the helium on the glass surface. A phenomenological model to account for these observations is proposed.The mechanism responsible for the relaxation of 3He on metallic surfaces remains obscure.
The present work examines the interaction of propanoic acid and I-propanol, I-butanol, I-ethanol, and I-hexanol with clean, oxidized, and anodized aluminum to identify the nature of the chemical bond on these surfaces. The investigations were carried out by x-ray photoelectron spectroscopy, at temperatures ranging from -20 to 500 ·C. Initially at room temperature, chemisorbed acid molecules break up on clean AI, leading to attachment of aliphatic chain fragments to the surface via carbon atoms. As adsorption continues, acid molecules react with Al via the functional group to oxidize the surface. In contrast, aliphatic alcohols chemisorb on clean AI via the functional group alone. At elevated temperatures, the acid and alcohols dissociate on the clean surface along similar reaction paths. On oxidized and anodized surfaces, the acid and alcohols chemisorb via the functional group and desorb at elevated temperatures without molecular dissociation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.