Study of the structure of helium films in nanoengineered pores.

Ordered templated porous materials such as MCM-41 offer an attractive platform for studying the effects of reduced dimensionality. Unfortunately, the attainable minimum pore diameters in these materials are still too large to reach the one-dimensional limit for helium. Recently Nichols et al have suggested that preplating MCM-41 pores with a rare gas can effectively reduce the effective pore diameter and modify the helium-pore interactions sufficiently to allow one-dimensional behavior to be observed. We have carried out small angle neutron scattering (SANS) studies of the adsorption of helium in argon preplated pores of MCM-41. Templated ordered materials such as MCM-41 have an ordered array of 1D pores and SANS yields a series of diffraction peaks determined by the inter-pore spacing. The intensity of these diffraction peaks yields information on the radial density within the pores. We will present results for the growth of argon layers and for the growth of helium in pores preplated with a monolayer of helium