Publications de Wolfgang Harbich

Chattez avec Graph Search

Posez n’importe quelle question sur les cours, conférences, exercices, recherches, actualités, etc. de l’EPFL ou essayez les exemples de questions ci-dessous.

AVERTISSEMENT : Le chatbot Graph n'est pas programmé pour fournir des réponses explicites ou catégoriques à vos questions. Il transforme plutôt vos questions en demandes API qui sont distribuées aux différents services informatiques officiellement administrés par l'EPFL. Son but est uniquement de collecter et de recommander des références pertinentes à des contenus que vous pouvez explorer pour vous aider à répondre à vos questions.

We present optical absorption and fluorescence spectra in the UV-visible range of size selected neutral Ag-n clusters (n = 1-9) in solid neon. Rich and detailed optical spectra are found with linewidths as small as 50 meV. These spectra are compared to tim ...

Thermal helium scattering is used to characterize the deposition of silver atoms on Pd (100) in the coverage range 0 to 10% of a monolayer, at surface temperature between 80 and 160 K, the latter being the threshold of adatom mobility. The attenuation of t ...

We report for the first time the absorption and fluorescence spectra of gold dimers in a neon matrix. The dimer absorption spectra show the A←X transition predicted from measurements in the gas phase and not observed so far in a matrix, as well as the so-c ...

The interaction between 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) and rare gas or para-hydrogen samples is studied by means of laser-induced fluorescence excitation spectroscopy. The comparison between spectra of PTCDA embedded in a neon matr ...

Thermal energy helium scattering is used to measure the isothermal desorption of NO from Pt(111) in the temperature range 343-383 K. Taking into account the vibrational degrees of freedom to calculate the residence time of the molecules, the energy of adso ...

We present optical absorption spectra in the UV-visible range (1.6 eV < omega < 5.5 eV) of mass selected neutral copper clusters Cu-n(n = 1-9) embedded in a solid neon matrix at 7 K. The atom and the dimer have already been measured in neon ma ...

We report on a home-built detector for catalytic reaction measurements offering good gas isolation from the surrounding ultrahigh vacuum components, high sensitivity for reaction products and a fast response time of 10 ms enabling dynamic studies correlated to reactant gas pulses. The device is mounted in ultrahigh vacuum and combined with a low-temperature scanning tunneling microscope and a source for the deposition of mass-selected clusters. This combination allows for a direct correlation between surfac

We present a new method to determine surface diffusion constants using specular reflected thermal helium scattering. The specular reflected helium intensity is recorded in real time as a function of surface coverage of the adsorbate and surface temperature ...

We present a new experiment to monitor ionized atom and mass selected cluster depositions in real time using specular reflected thermal helium scattering. Monomer Ag ions with an incident kinetic energy of E/sub dep/=20 eV and E/sub dep/=95 eV create surfa ...

Mass selected Ag/sub n/ clusters (n=1,7,19) from a secondary ion source have been deposited onto a Pt(111) substrate at low temperature. The surface and resulting cluster morphology have subsequently been characterized within the same UHV chamber by variable temperature STM as a function of cluster size, kinetic impact energy, and substrate temperature. The kinetic energy per cluster atom was found to be the decisive parameter for a controlled deposition. Noble gas buffer layers ( approximately=10 ML Ar), w

Clusters of metal atoms at a fixed size can assume different structural arrangements, known as isomers, which may have nearly the same energy. Therefore at given experimental conditions distribution of these isomers can be present. While the size selection is a relatively common technique, the isomer selection is not; it is therefore more difficult to obtain information about a single isomer. We report here on isomer specific spectroscopy of Ag9 clusters together with ab initio calculations allowing to iden

We present a new experiment which is able to monitor mass-selected cluster depositions in red time using specular reflected thermal helium scattering. Ag/sub 7//sup +/ with an incident energy of 2.86 and of 13.6 eV/atom is deposited on Pd(100) at different ...

A new method to measure the diffusion of adsorbed molecules over macroscopic distance on single crystal surfaces is presented and demonstrated with the system CO on Pt(111). A controlled coverage of molecules, typically of the order of 0.01 monolayer, is d ...

Light emission during the collision of ions and cluster ions on a metal surface covered by rare gas matrices of variable thickness is reported. The light intensity as a function of distance from the metal surface follows the classical image dipole theory. ...

We report on the growth of palladium nanoparticles on the basal plane of as-cleaved highly oriented pyrolytic graphite (HOPG) samples, and on CO2 ion sputtered nanostructured HOPG surfaces. The morphology of Pd nanostructures grown at room temperature is i ...

Oxidation catalysis on reducible oxide-supported small metal clusters often involves lattice oxygen. The present work aims at differentiating whether the reaction takes place at the cluster/support interface or on the cluster. To that purpose, we trace the ...

Electrochemical promotion of CO combustion over Pt/YSZ was investigated under high vacuum conditions. A galvanostatic step was coupled to mass spectrometric gas analysis using an electrochemical mass spectrometric monitoring device. Non-Faradaic electrochemical promotion of catalysis took place at 300 degrees C while only electrochemical oxidation was observed at 400 degrees C. Oxygen evolution measurements revealed that electrochemical promotion is related to the thermodynamically stable PtOx species over

We study the deposition and the very first steps of nucleation and growth of Ag on Pd(100) with thermal energy atom scattering. This technique is a very sensitive and nonperturbing probe to surface point defects, which permits an in situ and in-time monitoring of the deposition. The intention of this paper is to give a detailed description of the approach used in our work. The form of the specularly reflected helium signal as a function of coverage and surface temperature is compared to a theoretical curve,

We present optical absorption spectra from the ultraviolet to the visible for size selected neutral Ag-n clusters (n = 5-120) embedded in solid Ne. We compare the spectra to time-dependent density functional calculations (TDDFT) that address the influence ...

We study the deposition of Ag ions, and size selected Ag/sub 7/ and Ag/sub 19/ cluster ions on Pd(100) at total kinetic energies of 20 eV and 95 eV using thermal energy atom scattering and molecular dynamics simulations. We find that at all energies Ag atoms are implanted into the substrate and Pd atoms are ejected in the adlayer. The experimental results in the case of Ag/sub 7/ can be understood in taking into account both implantation of Ag atoms and heavy fragmentation. In the case of Ag/sub 19/ the dep

Wolfgang Harbich

Chattez avec Graph Search

Ultraviolet-visible absorption of small silver clusters in neon: Ag-n (n=1-9)

Neighbor driven mobility of silver adatoms on Pd(100) measured by thermal helium scattering

Gold dimer in neon: an absorption and fluorescence study

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Chemisorption and macroscopic diffusion of NO on Pt(111)

Optical absorption of small copper clusters in neon: Cu-n, (n=1-9)

An experimental setup combining a highly sensitive detector for reaction products with a mass-selected cluster source and a low-temperature STM for advanced nanocatalysis measurements

Surface diffusion of Ag on Pd(100) measured with specular helium scattering

The fate of mass selected silver clusters deposited on Pd(100)

Hard and soft landing of mass selected Ag clusters on Pt(111)

Isomer specific spectroscopy of metal clusters trapped in a matrix: Ag9

Mass-selected deposition of Ag 7 on Pd(100). Evidence for implantation and strong fragmentation

Measurement of macroscopic diffusion of CO on Pt(111) by thermal helium scattering

Collision-induced luminescence from the impact of ions and cluster ions on solid rare gases

Growth of palladium nanoparticles on nanostructured highly ordered pyrolytic graphite

Cluster Catalysis with Lattice Oxygen: Tracing Oxygen Transport from a Magnetite (001) Support onto Small Pt Clusters

Electrochemical promotion of CO combustion over Pt/YSZ under high vacuum conditions

Surface mobility of Ag on Pd(100) measured by specular helium scattering

Optical properties of size selected neutral Ag clusters: electronic shell structures and the surface plasmon resonance

Size selected cluster deposition on well characterized surfaces: Ag_n/Pd(100)