ALOISA

Welcome to the Advanced Line for Overlayer, Interface and Surface Analysis

In summer 2016, the original wiggler/undulator of ALOISA has been replaced by a new undulator. The new photon energy range is about 130-1500 eV (with the storage ring operated at 2.0 GeV).
X-Ray Diffraction experiments are no longer feasible.

Research Highlights

Intrinsic Nature of the Excess Electron Distribution at the TiO2 (110) Surface

The deposition of Na on the TiO2(110) surface injects
charge into Ti atoms originating a new electronic state in
the band gap, similar to the well-known Defect State due
to oxygen vacancies. In order to spatially localize the injected
charge, we have performed RESPED (Resonant Photoelectron
Diffraction) measurements of the valence band. The RESPED
from the stoichiometric, albeit Na-doped, surface is identical to
that obtained from the reduced surface. This evidence points to
a general property of TiO2(110), that is the redistribution of the
excess of charge is independent of the injection mechanism.
P. Kruger, et al. prl.aps.org/pdf/PRL/v108/i12/e126803

The gap state that appears upon reduction of TiO2 plays a key role in many of titania’s interesting properties but its origin and spatial localization have remained unclear. In the present work, the TiO₂(110) surface is reduced in a chemically controlled way by sodium adsorption. By means of resonant photoelectron diffraction, excess electrons are shown to be distributed mainly on subsurface Ti sites strikingly similar to the defective TiO₂
(110) surface, while any significant contribution from interstitial Ti ions is discarded.
  In agreement with first principles calculations, these findings demonstrate that the distribution of the band gap charge is an intrinsic property of TiO2(110), independent of the way excess electrons areproduced.

Retrieve article Intrinsic Nature of the Excess Electron Distribution at the TiO2 (110) Surface, P. Kruger, J. Jupille, S. Bourgeois, B. Domenichini, A. Verdini, L. Floreano, and A. Morgante PRL 108, 126803 (2012)
http://prl.aps.org/pdf/PRL/v108/i12/e126803

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Donor–Acceptor Shape Matching Drives Performance in Photovoltaics

Shape-complementarity of donor and acceptor molecules drives self-assembly into an extended interface with a ball-and-socket structural motif, which increases both the active volume and exciton dissociation rates to improve the efficiency of organic solar cells.
T. Schiros, et al. http://onlinelibrary.wiley.com/doi/10.1002/aenm.201201125/pdf

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Quantifying Through-Space Charge Transfer Dynamics in π-Coupled Molecular Systems

This work probes the relation between the rate of charge delocalization and the strength of through-space π-π coupling in stacked aromatic systems. With resonant photoemission we determine charge transfer (CT) dynamics in two molecular bi-layer systems with different inter-ring separation, [2,2]paracyclophane (22PCP) and [4,4]paracyclophane (44PCP) adsorbed on Au(111), which allows us to quantitatively probe the carrier transport as a function of inter-ring coupling strength. A.Batra et al.; http://www.nature.com/ncomms/journal/v3/n9/full/ncomms2083.html

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Tuning the catalytic activity of Ag(110) supported Fe-phthalocyanine in the oxygen reduction reaction

A careful choice of the surface coverage of Fe-phthalocyanine (FePc) on Ag (110) around the single monolayer allows us to drive with high precision both the long-range supramolecular arrangement and the local adsorption geometry of FePc molecules on the given surface.We show that this opens up the possibility of sharply switching the catalytic activity of FePc in the oxygen reduction reaction in a reproducible way. F. Sedona, et al. http://www.nature.com/nmat/journal/v11/n11/pdf/nmat3453.pdf

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Covalent Bonding in Surface-Confined Ullmann Polymerization

Surface polymerization is of great interest as it enables the realization of graphene-like layers with tunable properties by simply modifying the architecture of the molecular building blocks used as precursors. We focus on some open points concerning the fundamentals of surface-catalyzed dehalogenative polymerization based on Ullmann coupling, widely used over the past decade to obtain 1D and 2D polymers on surfaces. M. Di Giovannantonio et al. ACS Nano 7 (9), 8190 (2013)
http://pubs.acs.org/doi/abs/10.1021/nn4035684

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Trimethyltin-Mediated Covalent Gold–Carbon Bond Formation

Spectroscopic evidence of C-Au bond formation, responsible for the “electron gateway” state, is shown in the process of TrimethylTin break-up on gold.

A.Batra et al., J. Am. Chem. Soc., 2014, 136 (36), pp 12556–12559

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 Proposal Submission 

The Users must contact in advance the beamline responsible to evaluate 1) the proposal feasibility and 2) the most appropriate Review Panel. The local contact can also help the Users to single out which alternative beamlines are better suited to their requirements. We invite Users and collaborators to discuss their proposals with the beamline staff before the submission deadline.