Novel 1- and 2-Dimensional Systems

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This project will investigate novel thermodynamic and structural properties of atoms and molecules deposited (adsorbed) on single-wall carbon nanotube (SWNT) bundles and other surfaces. Nanometer-size, low dimensionality systems are at the forefront of research on new states of matter. SWNT bundles and other uniform substrates have made possible the fabrication of one- and two-dimensional (1d, 2d) forms of matter by adsorption of atoms/molecules on their surface. Heat of adsorption, heat capacity and X-ray scattering measurements are used to study several systems: (a) 1d helium, expected to remain in a single fluid phase down to absolute zero, (b) 1d molecular hydrogen, which may remain fluid to very low temperatures, (c) 1d and 2d crystals formed by Ar, Kr, and Xe, (d) 1d and 2d oxygen expected to show a crossover from 2d to 1d magnetic properties, and (e) quantum effects on the 2d phases of helium isotopic mixtures. SWNT bundles show promise for hydrogen storage, a matter of high technological importance addressed in this program. Participating graduate and undergraduate students learn a broad range of modern experimental techniques that position them well for future employment. Nanometer size, low dimensionality systems are at the forefront of research on novel fluid and solid states of matter. This experimental work focuses on measurements of the one- and two-dimensional (1d, 2d) properties of simple gases and molecules deposited (adsorbed) on single-wall carbon nanotube (SWNT) bundles, and the 2d properties of helium isotopic mixtures adsorbed on very small flat surfaces. Thermal and X-ray measurements characterize the phases and phase changes of the adsorbed substances as a function of temperature and density. Fascinating novel systems are: 1d helium which should remain in a single fluid phase at all temperatures, 1d molecular hydrogen which may remain fluid to very low temperatures, 1d and 2d Ar, Kr, and Xe which show solid structures being formed on the bundles, 1d and 2d oxygen with possible crossover from 2d to 1d magnetic properties, and the 2d properties of helium isotopic mixtures and their pronounced quantum effects. Bundles show promise for hydrogen storage, a matter of considerable technological importance. Participating graduate and undergraduate students acquire an array of modern experimental skills that position them well for future employment in any sector.