Probing liquid surfaces under vacuum using SEM and ToF-SIMS.

We report a newly developed self-contained interface for high-vapor pressure liquid surfaces to vacuum-based analytical instruments. It requires no wires or tubing connections to the outside of the instrument and uses a microfluidic channel with a 3 μm diameter window into the flowing fluid beneath it. This window supports the liquid against the vacuum by the liquid's surface tension and limits the high-density vapor region traversed by the probe beams to only a few microns.

The oil-water interface: mapping the solvation potential.

An ion moving across an oil-water interface experiences strong solvation changes. We have directly measured the solvation potential from 0.4 to 4 nm for Cs(+) ions approaching the oil-water interface from the oil side ("oil" = 3-methylpentane).

Pyroelectricity of water ice.

Water ice usually is thought to have zero pyroelectricity by symmetry. However, biasing it with ions breaks the symmetry because of the induced partial dipole alignment. This unmasks a large pyroelectricity.

Design and performance of an instrument for soft landing of biomolecular ions on surfaces.

A new ion deposition apparatus was designed and constructed in our laboratory. Our research objectives were to investigate interactions of biomolecules with hydrophilic and hydrophobic surfaces and to carry out exploratory experiments aimed at highly selective deposition of spatially defined and uniquely selected biological molecules on surfaces. The apparatus includes a high-transmission electrospray ion source, a quadrupole mass filter, a bending quadrupole that deflects the ion beam and prevents neutral molecules originating in the ion source from impacting the surface, an ultrahigh vacuum (UHV) chamber for ion deposition by soft landing, and a vacuum lock system for introducing surfaces into the UHV chamber without breaking vacuum.

Hydronium ion motion in nanometer 3-methyl-pentane films.

An ion soft-landing approach was applied to study the motion of hydronium (D(3)O(+)) and cesium (Cs(+)) ions from 84 to 104 K in glassy 3-methyl-pentane (3MP) films vapor deposited on Pt(111). Both ions were found to have very similar mobilities in 3MP. The span of ion mobilities probed is from approximately 10(-18) to approximately 10(-13) m(2) V(-1) s(-1).

Dissociation of water buried under ice on Pt(111).

Water on Pt(111) is generally thought to be nondissociative. However, by adsorbing a thick ice film [>150 monolayers (ML)], substantial (approximately 0.16 to 1 ML) dissociation of the "buried water" occurs for T>151 K.

Direct observation of completely processed calcium carbonate dust particles.

This study presents, for the first time, field evidence of complete, irreversible processing of solid calcium carbonate (calcite)-containing particles and quantitative formation of liquid calcium nitrate particles apparently as a result of heterogeneous reaction of calcium carbonate-containing mineral dust particles with gaseous nitric acid. Formation of nitrates from individual calcite and sea salt particles was followed as a function of time in aerosol samples collected at Shoresh, Israel. Morphology and compositional changes of individual particles were observed using conventional scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDX) and computer controlled SEM/EDX.

Nanometer-resolved interfacial fluidity.

Confined liquids can have properties that are poorly predicted from bulk parameters. We resolve with 0.5 nm resolution the nanoscale perturbations that interfaces cause on fluidity, in thin 3-methylpentane (3MP) films.

Quantitative time-resolved monitoring of nitrate formation in sea salt particles using a CCSEM/EDX single particle analysis.

Progress of the nitrate formation in individual sea salt particles was detected as a function of time using aerosol samples collected during the TexAQS 2080 experiment We demonstrate that the time-resolved collection approach coupled with the automated EDX single particle analysis made it possible to follow in detail the time evolution of sea salt particles within a diverse aerosol mixture. Using a custom built Time-Resolved Aerosol Collector (TRAC), particulate samples were taken sequentially on grid-supported 50 nm carbon films with a time resolution of 10 min between two consecutive samples. The samples were analyzed in the laboratory using Computer Controlled Scanning Electron Microscopy with Energy-Dispersed analysis of X-rays (CCSEM/EDX).