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Issue 21, 2008
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A combined droplet train and ambient pressure photoemission spectrometer for the investigation of liquid/vapor interfaces

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Abstract

We describe a combined ambient pressure photoelectron spectroscopy/droplet train apparatus for investigating the nature and heterogeneous chemistry of liquid/vapor interfaces. In this instrument a liquid droplet train with typical droplet diameters from 50–150 μm is produced by a vibrating orifice aerosol generator (VOAG). The droplets are irradiated by soft X-rays (100–1500 eV) in front of the entrance aperture of a differentially pumped electrostatic lens system that transfers the emitted electrons into a conventional hemispherical electron analyzer. The photoemission experiments are performed at background pressures of up to several Torr, which allows the study of environmentally important liquid/vapor interfaces, in particular aqueous solutions, under equilibrium conditions. The exposure time of the droplet surface to the background gases prior to the XPS measurement can be varied, which will allow future kinetic measurements of gas uptake on liquid surfaces. As an example, a measurement of the surface composition of a χ = 0.21 aqueous methanol solution is presented. The concentration of methanol at the vapor/liquid interface is enhanced by a factor of about 3 over the bulk value, while the expected bulk value is recovered at depths larger than about 1.5 nm.

Graphical abstract: A combined droplet train and ambient pressure photoemission spectrometer for the investigation of liquid/vapor interfaces

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Publication details

The article was received on 15 Jan 2008, accepted on 04 Mar 2008 and first published on 08 Apr 2008


Article type: Paper
DOI: 10.1039/B800717A
Citation: Phys. Chem. Chem. Phys., 2008,10, 3093-3098
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    A combined droplet train and ambient pressure photoemission spectrometer for the investigation of liquid/vapor interfaces

    D. E. Starr, E. K. Wong, D. R. Worsnop, K. R. Wilson and H. Bluhm, Phys. Chem. Chem. Phys., 2008, 10, 3093
    DOI: 10.1039/B800717A

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