The charge transfer of Rydberg hydrogen atoms at a metal surface is investigated for the first time. The surface ionization of Stark states with various electron density distributions with respect to the surface is examined. Unlike the nonhydrogenic species studied previously, genuine control over the orientation of the electronic wave function in the surface-ionization process is demonstrated. A comparison of the results for a range of collisional velocities for the most redshifted Stark state with principal quantum numbers n=20-36 with the classical over-the-barrier approach shows a good agreement for the onset of the ion signal, but the shallow rise in signal is not accounted for. An excellent fit of the experimental results can be achieved using a simple semiempirical model.

The influence of an acetamido group in directing the preferred choice of hydration sites in glucosamine and a consequent extension of the working rules governing regioselective hydration and conformational choice, have been revealed through comparisons between the conformations and structures of "free" and multiply hydrated phenyl N-acetyl-beta-D-glucosamine (betapGlcNAc) and phenyl beta-D-glucopyranoside (betapGlc), isolated in the gas phase at low temperatures. The structures have been assigned through infrared ion depletion spectroscopy conducted in a supersonic jet expansion, coupled with computational methods. The acetamido motif provides a hydration focus that overwhelms the directing role of the hydroxymethyl group; in multiply hydrated betapGlcNAc the water molecules are all located around the acetamido motif, on the "axial" faces of the pyranose ring rather than around its edge, despite the equatorial disposition of all the hydrophilic groups in the ring. The striking and unprecedented role of the C-2 acetamido group in controlling hydration structures may, in part, explain the differing and widespread roles of GlcNAc, and perhaps GalNAc, in nature.

Self-assembled mesoporous structures with well-ordered nanoscale channels could be used in applications such as molecular separation, nano-optics, molecular electronics, nanomedicine and catalysis. However, the domain sizes that can be created in such systems are limited by our lack of a detailed understanding of the relevant growth processes. Here we report the real-time observation of domain growth in the self-assembly of silica nanochannels using fluorescence polarization imaging and atomic force microscopy. We show that transient lamellar structures precede the formation of hexagonal layers, and that the layer growth follows two distinct pathways. In addition, the domains are grown on a mesoporous film substrate, which acts as a sieve and allows control of the delivery of the reactive species. We use these insights and capabilities to grow layers of well-ordered silica nanochannels with domain sizes of up to ∼0.3 mm.

The charge transfer (ionization) of hydrogen Rydberg atoms (n = 25 − 34) at a Cu(100) surface is investigated. Unlike fully metallic surfaces, where the Rydberg electron energy is degenerate with the conduction band of the metal, the Cu(100) surface has a projected bandgap at these energies, and only discrete image states are available through which charge transfer can take place. Resonant enhancement of charge transfer is observed for Rydberg states whose energy matches one of the image states, and the integrated surface ionization signals (signal versus applied field) show clear periodicity as a function of n as the energies come in and out of resonance with the image states. The surface ionization dynamics show a velocity dependence; decreased velocity of the incident H atom leads to a greater mean distance of ionization and a lower field required to extract the ion. The surface-ionization profiles for 'on resonance' n values show a changing shape as the velocity is changed, reflecting the finite field range over which resonance occurs.The collision of a Rydberg atom in the gas phase with a solid surface typically leads to transfer of the Rydberg electron to the surface at distances less than 5n 2 a 0 , where n is the Rydberg electron principal quantum number. This is especially true for metallic surfaces, where the Rydberg electron energy is degenerate with the conduction band so that resonant charge transfer (RCT) can occur. Experimental and theoretical studies of this phenomenon have focused on the effects of varying the n quantum number, the parabolic quantum number k, the velocity of the incoming particle and the applied fields [1,2], and observing how the rate of ionization varies as a function of distance from the surface [3]. For nonhydrogenic atoms, adiabatic and non-adiabatic passage through surface-induced energy level crossings leads to behavior that varies with the Rydberg species [4]. Thus, such studies reveal important information about the Rydberg states and their dynamics near surfaces.An equally important question for such studies is what they reveal about the nature of the surface. Experimental studies have been primarily conducted with flat-metal surfaces for which the ionization dynamics are almost independent of the material because of the generic behavior of RCT to the conduction band. However, there have also been some experimental and/or theoretical investigations of the effects of adlayers and thin insulating films [5], interaction with doped semiconductor surfaces [6] and dielectric materials [7], effects of corrugation and of patch charges [8,9]. Related theoretical calculations were used to investigate the variation of ionization rate of ground state H -with the thickness of a metal film substrate [10]. All these studies point to a degree of sensitivity of the charge transfer process to the surface characteristics. The mean radius of a hydrogenic Rydberg orbit is of order n 2 a 0 (e.g., ∼ 20 nm for n = 20) and charge transfer typically occurs at a Rydberg-surface distance of 3 − 5...