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Determination of the coverage dependent isosteric heat of adsorption of CO on Rh(1 1 1) by high resolution core level photoemission

High resolution core level photoemission is used to measure the equilibrium coverages of CO on Rh(1 1 1) at different sample temperatures and CO background pressures. Use of the chemical shifts of the C Is binding energy allows us to divide the total CO coverage into separate coverages for the different adsorption sites of CO on Rh(1 1 1). A Clausius-Clapeyron analysis of isosteres constructed fro

Beam line I411 at MAX II - Performance and first results

We report on the characteristics and first results from the soft X-ray beam line I411, based on an undulator at the third generation synchrotron facility MAX II, Sweden. The beam line is designed for high-resolution, angle-resolved electron spectroscopy on gases, liquids and solids. Main components are the modified SX700 monochromator and the end station, both of which were previously used at beam

Vibrationally resolved C Is photoemission from CO absorbed on Rh(1 1 1) : The investigation of a new chemically shifted C Is component

High-resolution core-level photoemission at an energy resolution better than the intrinsic width of the C 1s level has been used to study the CO/Rh(1 1 1) overlayer system. C Is spectra have been measured in a large CO coverage range; from low coverages, where the CO molecules only adsorb in on-top positions, to saturation coverage, where CO molecules occupy both on-top and threefold hollow sites.

Strong phonon replicas in Be 1s photoemission spectra

Strong phonon replicas in Be 1s photoemission spectra were investigated. The fine structure caused by intrinsic excitation of a narrow band of optical phonons was discussed in the 1s photoemission proces. The excitations of the optical Be phonons in the photoemission process caused fine structures. It was found that the phonon replicas in Be metal were strong due to large size misfit between neutr

Vibrational analysis of the C 1s photoemission spectra from pure ethylidyne and ethylidyne coadsorbed with carbon monoxide on Rh (111)

High-resolution core-level photoemission with a resolution better than the intrinsic width of the C 1s level has been used to study pure and coadsorbed ethylidyne overlayers on Rh(111). Components due to excitation of the C-H stretch vibration are clearly resolved in the C 1s spectra. In addition, a component due to the C-C vibration of the ethylidyne molecules is identified. The asymmetry paramet

Beyond ΛCDM : Problems, solutions, and the road ahead

Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in

Identification of a laterally mobile state during CO adsorption

We have investigated CO adsorption at 300 K on ∼ 1.5 atomic layer thick Pd films on a Mo(110) surface by high-resolution core level photoemission. We describe how high-resolution core level spectroscopy may be utilized to study the influence of laterally mobile states on the sticking probability of molecules on such a laterally heterogeneous surface. The present Pd films are laterally heterogeneou

Characterization of undulator radiation at MAXII using a soft X-ray fluorescence spectrometer

A grazing-incidence grating spectrometer has been used for the investigation of the undulator radiation from beamline 411 at MAX-lab. The direct detection of undulator light is expected to obtain the information of the quality of the undulator. Regular undulator radiation and some higher harmonics were observed. The effects of electronic beam coupling and Landau cavities have been studied. The exp

Soft-x-ray polarimeter with multilayer optics : Complete analysis of the polarization state of light

The design of a versatile high-precision eight-axis ultrahigh-vacuum-compatible polarimeter is presented. This multipurpose instrument can be used as a self-calibrating polarization detector for linearly and circularly polarized UV and soft-x-ray light. It can also be used for the characterization of reflection or transmission properties (reflectometer) or polarizing and phase-retarding properties

Adsorption sites in O and CO coadsorption phases on Rh(111) investigated by high-resolution core-level photoemission

High-resolution core-level spectroscopy is used in combination with low-energy electron diffraction (LEED) and photoelectron diffraction to identify the adsorption sites for three different coadsorbed phases consisting of ordered overlayers of oxygen coadsorbed with CO on the Rh(111) single-crystal surface. The three ordered overlayer structures, which may be denoted as 2O + CO/Rh(111), O + CO/Rh(

Soft x-ray undulator beam line 1411 at MAX-II for gases, liquids and solid samples

We report on the build-up of the new undulator beam line 1411 at the third-generation synchrotron radiation facility MAX II in Lund, Sweden. This beam line is based on an upgraded version of the modified SX700-monochromator and the end station which were installed previously at beam line 51 at MAX I. The end station is equipped with a rotatable Scienta hemispherical electron-analyser making angle-

Beamline 1511 at MAX II, capabilities and performance

The new undulator beamline 1511 at MAX-lab, now under commissioning, has been optimized for X-ray emission and photoelectron spectroscopies. Using an SX-700 high flux monochromator the accessible photon energy range is from 90 eV to about 1500 eV. The performance of the undulator agrees very well with the specifications, as shown by measurements using a photodiode. The energy resolution of the mon

Vibrational fine structure in the C 1s photoemission spectrum of the methoxy species chemisorbed on Cu(100)

The C 1s photoemission spectrum of methoxy (CH3O) chemisorbed on Cu(100) is demonstrated to contain a resolvable fine structure due to excitation of the molecular C-H normal vibrational mode. The origin of the fine structure is ascertained by substituting hydrogen with deuterium in the methoxy overlayers and by comparison to gas-phase C 1s spectra for methanol (CH3OH). The vibrational fine structu

Coverage- and temperature-dependent site occupancy of carbon monoxide on Rh(111) studied by high-resolution core-level photoemission

High-resolution core-level photoemission is used to study structural aspects for the molecular adsorption of CO on the Rh(111) single-crystal surface, and in particular to derive the adsorption sites. The site sensitivity of the core-level binding energy and the fact that the core level photoemission signal is proportional to the adsorbate coverage make it possible to study quantitatively how the

The influence of preadsorbed oxygen on the adsorption of CO on two-dimensional Pd islands on a Rh (111) surface

The influence of preadsorbed oxygen on the CO adsorption properties of a laterally heterogeneous bimetallic surface consisting of Pd islands on Rh(111) at a Pd coverage of 0.5 monolayers has been studied by high resolution core level photoemission. A surface consisting of clean Pd islands surrounded by oxygen-covered Rh(111) patches was prepared by predosing oxygen at room temperature. By applying

Adsorption sites in coadsorption systems determined by photoemission spectroscopy : K and CO coadsorbed on Rh(111)

The adsorption sites of coadsorbed K and CO on the Rh(111) surface have been determined using high-resolution core-level spectroscopy, low-energy electron diffraction and site-resolved photoelectron diffraction. For both a (2 × 2)-2CO-1K and a (2√3 × 2√3)-6CO-1K structure, we find that the CO molecules occupy threefold hollow sites and the K atoms on-top sites, contrary to the adsorption sites of

Förflyttning vid utrymning : en utvärdering av mätmetoder

Accurate measurement of people’s movement patterns during evacuation requires appropriate data collection methods. This study examines three different methods, namely cameras placed above the crowd, triangulation using two cameras and distance measurements with laser scanners. Experiments were performed both in the laboratory and the field in order to evaluate the different methods. The results su

Observation of a low-energy adsorbate core-level satellite for CO bonded to palladium : Coordination-dependent effects

A strong low-energy shake-up satellite for CO adsorbed on Pd is observed. The occurrence of the satellite is established for the CO/1 ML Pd/Mo(110) system at a coverage where CO adsorbs exclusively on-top. Comparisons with CO adsorbed on Pd single-crystal surfaces and small supported Pd particles indicate that the strongly increased satellite intensity is due to the decreased CO-Pd interaction str

Adsorption of acetylene and hydrogen on Pd(111) : Formation of a well-ordered ethylidyne overlayer

The C2H2(+H)/Pd(111) system has been studied using high resolution core level spectroscopy and low energy electron diffraction (LEED). Two ordered phases were found when adsorbing C2H2 at 125 K, giving rise to a (2 × 2) and a (√3 × √3)R30° LEED pattern, respectively. When preadsorbing H at 110-150 K, the sticking probability of the C2H2 molecules is strongly reduced and only the (√3 × √3)R30° over