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Topic: Photoemission spectroscopy

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  Physical Review B
Detection of weak emergent broken-symmetries of the kagome antiferromagnet by Raman spectroscopy
Spectroscopy of Eu^{3+} ions in congruent strontium barium niobate crystals
We report an angle-resolved photoemission study of the two-dimensional Fermi surface of the low-temperature phase.
prb.aps.org   (8890 words)

  Spectroscopy - Wikipedia, the free encyclopedia
Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation.
Spectroscopy is often used in physical and analytical chemistry for the identification of substances through the spectrum emitted from them or absorbed in them.
Thermal infrared spectroscopy measures thermal radiation emitted from materials and surfaces and is used to determine the type of bonds present in a sample as well as their lattice environment.
en.wikipedia.org /wiki/Spectroscopy   (1983 words)

 Photoemission spectroscopy - Wikipedia, the free encyclopedia
X-Ray Photoemission Spectroscopy (XPS, formerly known as ESCA - Electron Spectroscopy for Chemical Analysis) was developed at Uppsala University, Sweden in the 1960s by a group headed by Kai Siegbahn, who in 1981 won the Nobel Prize for Physics for his work in developing the technique.
An article on X-ray photoelectron spectroscopy that complements this article is located elsewhere.
Photoemission Spectroscopy (PES) may also refer to a technique devised by Richard Smalley.
en.wikipedia.org /wiki/Photoemission_spectroscopy   (863 words)

 Spectroscopy Summary
The effects governing x-ray photoelectron spectroscopy were first explained by German-American physicist Albert Einstein (1879–1955) in 1905, who showed that the energy of an electron ejected in photoemission was equal to the difference between the photon and the binding energy of the electron in the target.
Spectroscopy is not confined to the realms of visible light.
Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency.
www.bookrags.com /Spectroscopy   (6000 words)

 Group Members
X-ray photoelectron spectroscopy (XPS) is to determine the composition and chemical states of ultra-thin film (£ 4 nm), since the film thickness was comparable to the escape length of photoelectrons.
The photoemission intensity of each element measured by XPS depends upon the depth from which the photoelectron is emitted and represents an exponentially attenuated convolution of the actual composition depth profile of the sampled area.
A maximum entropy routine was used to convert the angle dependent photoemission intensities to compositions as a function of depth.
www.chemeng.ucla.edu /jchang/Chang-XPS.htm   (355 words)

 Beamline Technique 01: Low-Energy Spectroscopy
PURPOSE: Probes that use the VUV region of the spectrum (10–100 eV) are very well matched to the elucidation of bonding in solids, surfaces, and molecules; to the investigation of electron–electron correlations in solids, atoms, and ions; and to the study of reaction pathways in chemical dynamics.
One of the most intriguing is a “dimensional crossover” in layered metals where, in the direction perpendicular to the layers, transport properties change from insulator-like at high temperatures to metallic-like at low temperatures, while remaining metallic over the whole temperature range in the direction parallel to the layers.
Recent photoemission experiments have shown that this change in effective dimensionality correlates with changes in the electronic spectra: sharp features associated with “quasiparticle-like excitations” only exist in the low-temperature three-dimensional-like phase, while they are absent in the effectively two-dimensional, high-temperature phase.
www.er.doe.gov /bes/synchrotron_techniques/spectroscopy01.htm   (1344 words)

 Beamline Technique 02: Soft X-Ray Spectroscopy
From the data obtained, the researchers concluded that liquid water consists mainly of structures with two strong hydrogen bonds, in contrast to the four bonds found in the tetrahedral structure of ice.
Emission and absorption spectroscopy together reveal the optical gap in semiconductors, with emission revealing the valence band maximum and absorption revealing the conduction band minimum.
When a ferromagnet and an antiferromagnet are combined in a layered structure — such structures are part of the read heads in computer hard drives — the hard ferromagnet pins and holds the magnetization of the ferromagnet across the interface in the presence of an applied magnetic field, up to a certain field threshold.
www.er.doe.gov /bes/synchrotron_techniques/spectroscopy02.htm   (1062 words)

 Charles Thiel's Research on Rare-Earth-Activated Luminescent Materials
5d transitions, and photoionization and electron photoemission spectroscopy of the 4f electrons and host states are all employed to map out the energy levels and interactions that are crucial for technological applications as well as for a fundamental physical understanding of rare-earth-activated optical materials.
The primary difficulties in applying photoemission to the study of optical materials are the requirement of ion concentrations of at least a few atomic percent and complications arising from electrical charging due to the highly insulating nature of the materials being studied.
By supplementing photoemission with complementary techniques such as photoconductivity, excited state absorption, bremsstrahlung isochromat spectroscopy, and inverse photoemission, the relationships and interactions between rare earth ions and the occupied and unoccupied electronic states of the host crystal may be thoroughly explored.
www.physics.montana.edu /students/thiel/research.html   (5987 words)

 SLS Web Site - Research
Photoemission spectroscopy is known as a powerful technique to directly probe the occupied electronic structure, bonding and chemical nature of a material.
For 3d transition metal compounds, the 3d photoemission is strongly enhanced when the energy of the incoming light equals the energy necessary to excite an electron from the 3p core level to the unoccupied 3d state.
To map Fermi surfaces directly one measures the intensities of the photoelectrons emitted as a function of emission angles to the crystal axes, and thus of the momentum component k parallel to the surface.
sls.web.psi.ch /view.php/beamlines/sis/research/index.html   (788 words)

 ARPES 2005 - home
Angle-Resolved PhotoEmission Spectroscopy (ARPES) is the most direct method of studying the momentum dependent electronic structure of solids.
The second goal is to bring together the community of experts in the field of novel quantum materials, at the national and international level, who would directly benefit from the development of a new state-of-the-art facility for Spin and Angle-resolved Photoelectron Spectroscopy at the Canadian Light Source.
The invited scientists will contribute expertise in synchrotron based spectroscopes with specific emphasis on spin and angle-resolved photoemission, in the synthesis/fabrication of novel quantum materials and nanostructures for which ARPES is an ideal characterization tool, as well as in the most advanced theoretical schemes developed to describe the electronic properties of complex many-body systems.
www.ampel.ubc.ca /ARPES2005NF   (408 words)

 PHOTOEMISSION SPECTROSCOPY:Gaps, Pseudogaps, and Occam's Razor -- Arko 284 (5415): 752 -- Science
Angle-Resolved Photoelectron Spectroscopy, or ARPES, is an important tool which allows direct observation of occupied electron states in a material.
Recent advances in improving the resolution of this method, together with the vastly improved quality of crystals of many materials, have led to the observation of features such as gaps in the photoelectron spectrum which have been difficult to understand.
Arko discusses a paper by Joynt (page 777) which shows that the observed effects may be extrinsic, that is part of the photoemission process, rather than intrinsic to the material and thus requiring a new physical explanation.
www.sciencemag.org /cgi/content/short/284/5415/752   (261 words)

 X-ray photoemission spectroscopy
In analogy to valence band photoemission techniques x-ray photoelectron spectroscopy (XPS) uses the kinetic energy of the photoexcited electrons to derive the binding energy of the initial electronic state which is directly related to the ionization energy of the appropriate atomic orbital.
As these emissions, which are characterized by their binding energies, simply overlay each other in compounds or mixtures, ESCA (Electron Spectroscopy for Chemical Analysis) measurements allow the identification of all participating elements by determination of their atomic core level lines.
Therefore, high-resolution x-ray photoelectron spectroscopy is the preferred technique to trace chemical reactions or redox processes.
www.ieap.uni-kiel.de /surface/ag-skibowski/xps.htm   (498 words)

It is the electric vector which is involved in spectroscopy, since it is the component which couples with electrons to excite them.
In photoemission (also known as photoelectron) spectroscopy, energies are used to effect excitations that result in electrons transitioning from an initial quantum state to a free state, resulting in the electron being removed from an atom or molecule.
This is crucially important in angle resolved photoemission spectroscopy because the wave nature of photoelectrons is therefore a vector quantity from which direction and polarization can be determined (10).
www.sas.upenn.edu /~cogswell/Spec.project/spec_photoemiss_spec_works_theory.html   (730 words)

 Bartynski Group - Experimental - Photoemission and Inverse Photoemission
We primarily apply photoemission and inverse photoemission to examine the electronic states within a few eV below or above, respectively, the Fermi level of our sample.
We perform inverse photoemission spectroscopy in either of two modes.  In the isochromat mode, the incident electron energy is ramped between ~ 5 eV and 15 eV kinetic energy, while photons of a particular energy are detected.
The second, more versatile mode of inverse photoemission uses a grating spectrometer illustrated in the figure at the right.  In this case, electrons of a fixed energy are incident on the sample while photons produced by direct optical transitions are dispersed by a concave spherical diffraction grating and detected by a position sensitive microchannelplate array.
www.physics.rutgers.edu /~bart/home/PE_IPE_RAB.htm   (270 words)

 Experimental Physics Research
We believe that a core component in the graduate education in experimental physics is to provide students with a supportive environment in which they, after initial training, are able to find their own initiatives in pursuit of research interests, and eventually become the primary experts in their respective fields.
The study exploits a new kind of laser spectroscopy in which absorption of a photon leads to the detachment of a metastable particle from the surface.
Yana Reshetnyak is a biological physicist specializing in protein fluorescence spectroscopy, folding of membrane proteins, and the design and development of pH-sensitive delivery peptides.
www.phys.uri.edu /research/experiment.html   (952 words)

 [No title]
Lasers have been used for photoemission for many years, especially for the study of electron dynamics at surfaces.
While still very powerful, angle-integrated photoemission does not allow one to uncover the E vs. k (energy vs. momentum) dispersion relation of an electronic band state - information which is typically considered a starting point for understanding the electronic behavior of a solid.
The surface sensitivity of conventional photoemission is determined by the electron mean-free-path, which is the mean distance a photoelectron can travel between scattering events as it tries to leave the sample.
spot.colorado.edu /~dessau/LaserARPES.shtml   (759 words)

 X-ray absorption spectroscopy
While direct photoemission spectroscopy offers an experimental approach to to the occupied electronic bands of a solid state, XANES (x-ray absorption near-edge spectroscopy) or NEXAFS (near-edge x-ray absorption fine structure) is a technique to characterize surfaces by evaluation of unoccupied electronic states.
In contrast to inverse photoemission spectroscopy the experimental setup simply requires a monochromatically tunable light source and an electron energy analyzer so that XANES measurements can be performed at each synchrotron radiation source of sufficient energy.
Due to the sharp transitions in molecular systems near-edge absorption spectroscopy is one of the preferred experimental techniques to study organic thin films.
www.ieap.uni-kiel.de /surface/ag-kipp/xanes/xanes.htm   (731 words)

 Citebase - Quasi-particles and their absence in photoemission spectroscopy   (Site not responding. Last check: )
Photoemission spectroscopy of the single particle spectral function is a central experimental tool for such studies.
A general paradigm of quasi-particle formation is the Fermi level resonance associated with the Kondo physics of the Anderson impurity model, an effective self consisent version of which is utilized in dynamic mean field theories of general lattice systems which may or may not literally display Kondo physics.
This paper presents an overview of the theoretical ideas and shows examples in photoemission spectra, taken from the work of the author and his collaborators, of quasi-particle formation in impurity and lattice Kondo and non-Kondo correlated electron systems, contrasted with quasi-particle absence in a quasi-one-dimensional system.
www.citebase.org /abstract?id=oai:arXiv.org:cond-mat/0211098   (231 words)

 Space charge effect and mirror charge effect in photoemission spectroscopy
We report the observation and systematic investigation of the space charge effect and mirror charge effect in photoemission spectroscopy.
When pulsed light is incident on a sample, the photoemitted electrons experience energy redistribution after escaping from the surface because of the Coulomb interaction between them (space charge effect) and between photoemitted electrons and the distribution of mirror charges in the sample (mirror charge effect).
This value is comparable to many fundamental physical parameters actively studied by photoemission spectroscopy and should be taken seriously in interpreting photoemission data and in designing next generation experiments.
repositories.cdlib.org /lbnl/LBNL-56165   (211 words)

 Expert: Surface Science, Thin Films, Interactions of Ion Beams With Surfaces, Sputtering, Film Deposition Expert
He utilizes many spectroscopy techniques, including X-ray photoelectron, UV photoemission, Auger, ion scattering, and optical, to study these material surfaces.
Expert' Ph.D. research was in UV and visible absorption and emission spectroscopy, and he is very knowledgeable in molecular and atomic absorption, emission spectroscopy, flourescence, and phosphorescence.
Expert has experience in various analytical techniques, such as x-ray photoelectron spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, ion scattering spectrometry, mass spectrometry, low energy electron diffraction, optical absorption and emission spectroscopy, and infrared spectroscopy.
www.intota.com /viewbio.asp?bioID=603238&perID=108226   (1088 words)

 STM-excited electroluminescence and spectroscopy on organic materials for display applications
For instance, studies performed using techniques such as ultraviolet photoemission spectroscopy (UPS) [2–7], internal photoemission [8, 9], and scanning tunneling microscope (STM) spectroscopy [10–12] show clear evidence of significant deviations from the CVL rule for organic–metal and organic–organic interfaces.
A technique that allows the alignment of the empty states to be determined in a direct way is particularly welcome, because photoemission spectroscopy techniques have so far proved useful only as probes of the occupied levels of organic materials.
This is the model underlying the spectroscopy technique for the determination of the density of states in the surface region by means of i–V curves collected with the STM-feedback loop disconnected [23].
www.research.ibm.com /journal/rd/451/alvarado.html   (4736 words)

 CAU Kiel: Fermi-vector determination
If photoemission calculations including the complete physics (within the one-step model) are not available, practical procedures for an analysis of high resolution photoemission data are needed.
Employing high resolution photoemission spectroscopy we show how surface-parallel components of the Fermi vectors can be determined with high accuracy.
Intensity modifications due to the photoemission process are explicitly eliminated by comparing photoemission spectra taken at different temperatures.
www.tp.cau.de /schattke/pres/mr99_b.html   (753 words)

 The Actinide Research Quarterly: 4th Quarter 2000
This article describes the progress of our photoemission and EELS studies of Pu metal with the objective of understanding the electronic structure of this material and the unique changes it undergoes from low temperature to the liquid phase.
Analysis of the plasmon response of the material over the range of primary electron energies that were used shows substantial changes as the depth of material sampled by the spectroscopy changes from approximately 8 to 18 Å.
This measurement involves absorption of an x-ray or ultraviolet photon by an atom in the solid with corresponding ejection of a photoelectron from the surface of the material.
www.lanl.gov /orgs/nmt/nmtdo/AQarchive/00winter/recent.html   (1544 words)

 Current Research Projects of the Novel Materials Lab @ BU
Photoemission spectroscopy is a ubiquitous probe of electronic structure in solids, but photoemission studies of organic superconductors have met with limited success, and many important properties, such as Fermi surface structures, the density of states close to the Fermi level (E
We solve the beam damage and surface problems associated with earlier studies of single crystals by growing thin films of these materials in-situ, and continuously translating the films in front of the synchrotron radiation beam as spectra are recorded.
We are working towards two significant breakthroughs: definitive spectroscopic measurements of electronic structure in organic superconductors, and the development of methods to synthesize thin films of organic superconductors using organic molecular beam deposition techniques.
physics.bu.edu /~ksmith/esg.htg/Research.html   (1012 words)

 Session Y20 - Photoemission Studies of Cuprates and Related Materials.
Using high-resolution angle-resolved photoemission on BISCO we have studied the dispersion relations and photoemission line-shapes close to the Fermi level.
We demonstrate that recent angle resolved photoemission data in bilayer cuprate superconductors imply that scattering of electrons between bonding and antibonding bands is strong compared to scattering between these bands.
At finite x, the experimentally observed photoemission spectra are compatible with the ones of a model that does not contain any electron-phonon coupling, at least with the k-space resolution allowed by lattice size clusters up to 242 size.
flux.aps.org /meetings/YR03/MAR03/baps/abs/S9000.html   (2065 words)

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