The Experts below are selected from a list of 86163 Experts worldwide ranked by ideXlab platform
Sven Tougaard - One of the best experts on this subject based on the ideXlab platform.
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Surface Excitation parameter for allotropic forms of carbon
Surface and Interface Analysis, 2012Co-Authors: Nicolas Pauly, Mihaly Novak, Sven TougaardAbstract:The Surface Excitation parameter (SEP) is calculated for five carbon allotropes: amorphous carbon, graphite, glassy carbon, C60-fullerite and diamond for electron energies between 300 eV and 3400 eV, and for angles between 0° and 60° to the Surface normal. SEP, defined as the change in Excitation probability, for an electron, caused by the presence of the Surface in comparison with an electron moving the same distance in an infinite medium, is calculated within two dielectric response models due to Yubero and Tougaard (YT) and Tung, Chen, Kwei and Chou (TCKC) respectively. We show that SEP results obtained from TCKC are roughly independent of the allotrope while values calculated from YT are clearly material dependent. Moreover we find that SEP calculated from TCKC is on average 40% larger than those calculated from YT, the difference being largest for materials with large band gap energy. This difference is due to the simplified description of Surface Excitations in TCKC Copyright © 2012 John Wiley & Sons, Ltd.
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Comparison between Surface Excitation parameter obtained from QUEELS and SESINIPAC
Surface and Interface Analysis, 2012Co-Authors: Nicolas Pauly, Mihaly Novak, Alain Dubus, Sven TougaardAbstract:Surface Excitations significantly influence the measured peak intensities in elastic peak electron spectroscopy. They are characterised by the Surface Excitation parameter (SEP) defined as the change in Excitation probability of an electron caused by the presence of the Surface in comparison with an electron moving in an infinite medium. It is thus important to have a large database of SEP values or to have the possibility to determine it with a user-friendly software. Recently, Novak developed the programme Software for Electron Solid Inelastic Interaction Parameter Calculations (SESINIPAC) within the model of Tung, Chen, Kwei and Chou, which allows to determine inelastic mean free path, differential inelastic mean free path, SEP and differential SEP for various energy loss function models and dispersion relations with as only input the energy loss function of the material. Using SESINIPAC, we calculate SEP for 27 different types of materials (metals, semiconductors and insulators) and for various angles and energies. We compare these results with those obtained previously with the software Quantitative Analysis of Electron Energy Losses at Surfaces (QUEELS), which uses the Yubero-Tougaard model. We show that the dependence on angle of emission and energy is quite similar for the two models. However, the absolute values calculated with SESINIPAC are generally larger than those calculated with QUEELS, and the mean relative difference is 20% for metals and semiconductors but exceeds 50% for insulators. Copyright © 2012 John Wiley & Sons, Ltd.
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Core hole and Surface Excitation correction parameter for XPS peak intensities
Surface Science, 2011Co-Authors: Nicolas Pauly, Sven TougaardAbstract:Abstract In XPS analysis, Surface Excitations and Excitations originating from the static core hole created during the photoExcitation process are usually neglected. However, both effects significantly reduce the measured peak intensity. In this paper we have calculated these effects. Instead of considering the two effects separately, we introduce a new parameter, namely the Correction Parameter for XPS (or CPXPS) defined as the change in probability for emission of a photoelectron caused by the presence of the Surface and the core hole in comparison with the situation where the core hole is neglected and the electron travels the same distance in an infinite medium. The CPXPS calculations are performed within the dielectric response theory by means of the QUEELS-XPS software determining the energy-differential inelastic electron scattering cross-sections for X-ray photoelectron spectroscopy (XPS) including Surface and core hole effects. This study has been carried out for electron energies between 300 eV and 3400 eV, for angles to the Surface normal between 0° and 60° and for various materials, especially metals, semiconductors and oxides. For geometries and energies normally used in XPS, i.e. for emission angle ≤ 60° and photoelectron energy ≤ 1500 eV, we find that CPXPS values are significantly larger for oxides, (0.55 ≲ CPXPS ≲ 0.75) than for metals and semiconductors (0.45 ≲ CPXPS ≲ 0.6). We show that this behavior is due to the difference in the wave vector dispersion of the energy loss function. This dispersion has been determined from analysis of REELS and is found to be free electron like (α ≅ 1) for metals but is substantially smaller (α ≈ 0.02–0.05) for materials with a wide band gap. As a result, the group velocity of the valence electrons is very small for oxides with a large band gap. This leads to a reduction in the screening of the core-hole potential before the photoelectron has left the region of interaction and thereby to an increase in the intrinsic Excitations caused by the core hole.
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Surface Excitation parameter for 12 semiconductors and determination of a general predictive formula
Surface and Interface Analysis, 2009Co-Authors: Nicolas Pauly, Sven TougaardAbstract:The Surface Excitation parameter (SEP) is theoretically calculated for 12 semiconductors (GaN, GaP, GaSb, GaAs, InSb, InAs, InP, SiC, ZnSe, ZnS, Si and Ge) and for Ni (which is usually used as a reference in experiments) for electron energies between 300 eV and 3400 eV, and for angles between 0° and 70° to the Surface normal. We use our previous definition of SEP, as the change in Excitation probability, for an electron, caused by the presence of the Surface in comparison with an electron moving the same distance in an infinite medium. The calculations are performed within the dielectric response theory by means of the QUEELS-e(k, ω)-REELS software determining the energy-differential inelastic electron scattering cross-sections for reflection-electron-energy-loss spectroscopy (REELS), and for which the only input is the dielectric function of the medium. By fitting to these SEP values as well as our previous ones, i.e. from 27 materials, including metals, oxides, polymers and semiconductors, we also establish a simple equation depending on the generalized plasmon energy and the energy band gap of the material which allows to estimate the SEP when the dielectric function is not available. Copyright © 2009 John Wiley & Sons, Ltd.
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Calculation of the angular distribution of the Surface Excitation parameter for Ti, Fe, Cu, Pd, Ag and Au
Surface and Interface Analysis, 2008Co-Authors: Nicolas Pauly, Sven TougaardAbstract:We define Surface Excitation parameter (SEP) as the change in Excitation probability of an electron caused by the presence of the Surface in comparison with an infinite medium, and we calculate the angular dependence of the SEP for different metals (Ti, Fe, Cu, Pd, Ag, and Au), for angles to the Surface normal between 10° and 70° and for different energies. The calculations are based on a study of energy-differential inelastic electron scattering cross-sections obtained from the software Quantitative analysis of Electron Energy Losses at Surfaces (QUEELS) valid for reflection-electron-energy-loss spectroscopy (REELS). The intensity of the Surface Excitation is isolated from the total spectrum by subtracting the volume component for an infinite medium and the SEP is deduced from it. Copyright © 2008 John Wiley & Sons, Ltd.
Joshua C Vaughan - One of the best experts on this subject based on the ideXlab platform.
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Microscopy with ultraviolet Surface Excitation for wide-area pathology of breast surgical margins
Journal of biomedical optics, 2019Co-Authors: Weisi Xie, Ye Chen, Yu Wang, Linpeng Wei, Chengbo Yin, Adam K Glaser, Mark E Fauver, Eric J Seibel, Suzanne M Dintzis, Joshua C VaughanAbstract:Intraoperative assessment of breast surgical margins will be of value for reducing the rate of re-excision surgeries for lumpectomy patients. While frozen-section histology is used for intraoperative guidance of certain cancers, it provides limited sampling of the margin Surface (typically
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microscopy with ultraviolet Surface Excitation for wide area pathology of breast surgical margins
Journal of Biomedical Optics, 2019Co-Authors: Weisi Xie, Ye Chen, Yu Wang, Linpeng Wei, Chengbo Yin, Adam K Glaser, Mark E Fauver, Eric J Seibel, Suzanne M Dintzis, Joshua C VaughanAbstract:Intraoperative assessment of breast surgical margins will be of value for reducing the rate of re-excision surgeries for lumpectomy patients. While frozen-section histology is used for intraoperative guidance of certain cancers, it provides limited sampling of the margin Surface (typically <1 % of the margin) and is inferior to gold-standard histology, especially for fatty tissues that do not freeze well, such as breast specimens. Microscopy with ultraviolet Surface Excitation (MUSE) is a nondestructive superficial optical-sectioning technique that has the potential to enable rapid, high-resolution examination of excised margin Surfaces. Here, a MUSE system is developed with fully automated sample translation to image fresh tissue Surfaces over large areas and at multiple levels of defocus, at a rate of ∼5 min / cm2. Surface extraction is used to improve the comprehensiveness of Surface imaging, and 3-D deconvolution is used to improve resolution and contrast. In addition, an improved fluorescent analog of conventional H&E staining is developed to label fresh tissues within ∼5 min for MUSE imaging. We compare the image quality of our MUSE system with both frozen-section and conventional H&E histology, demonstrating the feasibility to provide microscopic visualization of breast margin Surfaces at speeds that are relevant for intraoperative use.
Stavros G Demos - One of the best experts on this subject based on the ideXlab platform.
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Microscopy with ultraviolet Surface Excitation (MUSE) enables translation of optical biopsy principles to enhance life science education
Optical Biopsy XVII: Toward Real-Time Spectroscopic Imaging and Diagnosis, 2019Co-Authors: Katherine A. Kopp, Stavros G Demos, Tanya Z. KoscAbstract:The translation of microscopy with ultraviolet Surface Excitation (MUSE) into a high school science classroom is investigated with the goal of providing a suitable new modality to enhance life science education. A key part of this effort is the development of laboratory exercises that can integrate the advanced capabilities of MUSE into a classroom setting. MUSE utilizes the unique property of ultraviolet light at wavelengths between 250 and 285 nm to propagate about 10 μm into tissues, thus illuminating only the top cell layer. This illumination is provided by a low-power UV LED source, which enables one to cost-efficiently implement this method into the educational environment. MUSE in education can eliminate the need for premade microscope slides and provide a far more engaging and rewarding experience for students.
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Adaptation of microscopy with ultraviolet Surface Excitation for enhancing STEM and undergraduate education
Journal of biomedical optics, 2018Co-Authors: Chi Z. R. Huang, Ronald W. Wood, Stavros G DemosAbstract:Microscopy with ultraviolet Surface Excitation (MUSE) is investigated as a means to enhance curricula and education in the life sciences based on simplicity of use, the incorporation of inexpensive hardware, and the simplest methods of tissue preparation. Ultraviolet Excitation in effect replaces tissue sectioning because it penetrates only a few micrometers below the tissue Surface at the single cell level, preventing the generation of out-of-focus light. Although tissue autofluorescence may be used, image quality and content can be enhanced by a brief immersion in a solution of nontoxic fluorescent dyes that selectively highlight different cellular compartments. Safe mixed-dye powder combinations have been developed to provide students who have minimal lab proficiencies with a one-step tissue staining process for rapid tissue preparation.
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microscopy with ultraviolet Surface Excitation for rapid slide free histology
Nature Biomedical Engineering, 2017Co-Authors: Farzad Fereidouni, Zachary Harmany, Miao Tian, Austin Todd, John A Kintner, John Douglas Mcpherson, Alexander D Borowsky, John W Bishop, Mirna Lechpammer, Stavros G DemosAbstract:Histologic examination of tissues is central to the diagnosis and management of neoplasms and many other diseases, and is a foundational technique for preclinical and basic research. However, commonly used bright-field microscopy requires prior preparation of micrometre-thick tissue sections mounted on glass slides, a process that can require hours or days, that contributes to cost, and that delays access to critical information. Here, we introduce a simple, non-destructive slide-free technique that within minutes provides high-resolution diagnostic histological images resembling those obtained from conventional haematoxylin-and-eosin-histology. The approach, which we named microscopy with ultraviolet Surface Excitation (MUSE), can also generate shape and colour-contrast information. MUSE relies on ~280-nm ultraviolet light to restrict the Excitation of conventional fluorescent stains to tissue Surfaces, and it has no significant effects on downstream molecular assays (including fluorescence in situ hybridization and RNA-seq). MUSE promises to improve the speed and efficiency of patient care in both state-of-the-art and low-resource settings, and to provide opportunities for rapid histology in research.
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Microscopy with ultraviolet Surface Excitation for rapid slide-free histology
Nature Biomedical Engineering, 2017Co-Authors: Farzad Fereidouni, Zachary Harmany, Miao Tian, Austin Todd, John A Kintner, John Douglas Mcpherson, Alexander D Borowsky, Mirna Lechpammer, John Bishop, Stavros G DemosAbstract:Histological examination of tissues is central to the diagnosis and management of neoplasms and many other diseases and is a foundational technique for preclinical and basic research. However, commonly used bright-field microscopy requires prior preparation of micrometre-thick tissue sections mounted on glass slides—a process that can require hours or days, contributes to cost and delays access to critical information. Here, we introduce a simple, non-destructive slide-free technique that, within minutes, provides high-resolution diagnostic histological images resembling those obtained from conventional haematoxylin and eosin histology. The approach, which we named microscopy with ultraviolet Surface Excitation (MUSE), can also generate shape and colour-contrast information. MUSE relies on ~280 nm ultraviolet light to restrict the Excitation of conventional fluorescent stains to tissue Surfaces and it has no significant effects on downstream molecular assays (including fluorescence in situ hybridization and RNA sequencing). MUSE promises to improve the speed and efficiency of patient care in both state-of-the-art and low-resource settings and to provide opportunities for rapid histology in research. A slide-free, inexpensive and non-destructive microscopy technique rapidly provides high-resolution histology images that resemble those obtained from conventional haematoxylin-and-eosin-stained specimens.
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Slide-free histology via MUSE: UV Surface Excitation microscopy for imaging unsectioned tissue(Conference Presentation)
Optical Biopsy XIV: Toward Real-Time Spectroscopic Imaging and Diagnosis, 2016Co-Authors: Richard M. Levenson, Stavros G Demos, Zachary Harmany, Farzad FereidouniAbstract:Widely used methods for preparing and viewing tissue specimens at microscopic resolution have not changed for over a century. They provide high-quality images but can involve time-frames of hours or even weeks, depending on logistics. There is increasing interest in slide-free methods for rapid tissue analysis that can both decrease turn-around times and reduce costs. One new approach is MUSE (microscopy with UV Surface Excitation), which exploits the shallow penetration of UV light to excite fluorescent signals from only the most superficial tissue elements. The method is non-destructive, and eliminates requirement for conventional histology processing, formalin fixation, paraffin embedding, or thin sectioning. It requires no lasers, confocal, multiphoton or optical coherence tomography optics. MUSE generates diagnostic-quality histological images that can be rendered to resemble conventional hematoxylin- and eosin-stained samples, with enhanced topographical information, from fresh or fixed, but unsectioned tissue, rapidly, with high resolution, simply and inexpensively. We anticipate that there could be widespread adoption in research facilities, hospital-based and stand-alone clinical settings, in local or regional pathology labs, as well as in low-resource environments.
Weisi Xie - One of the best experts on this subject based on the ideXlab platform.
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Microscopy with ultraviolet Surface Excitation for wide-area pathology of breast surgical margins
Journal of biomedical optics, 2019Co-Authors: Weisi Xie, Ye Chen, Yu Wang, Linpeng Wei, Chengbo Yin, Adam K Glaser, Mark E Fauver, Eric J Seibel, Suzanne M Dintzis, Joshua C VaughanAbstract:Intraoperative assessment of breast surgical margins will be of value for reducing the rate of re-excision surgeries for lumpectomy patients. While frozen-section histology is used for intraoperative guidance of certain cancers, it provides limited sampling of the margin Surface (typically
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microscopy with ultraviolet Surface Excitation for wide area pathology of breast surgical margins
Journal of Biomedical Optics, 2019Co-Authors: Weisi Xie, Ye Chen, Yu Wang, Linpeng Wei, Chengbo Yin, Adam K Glaser, Mark E Fauver, Eric J Seibel, Suzanne M Dintzis, Joshua C VaughanAbstract:Intraoperative assessment of breast surgical margins will be of value for reducing the rate of re-excision surgeries for lumpectomy patients. While frozen-section histology is used for intraoperative guidance of certain cancers, it provides limited sampling of the margin Surface (typically <1 % of the margin) and is inferior to gold-standard histology, especially for fatty tissues that do not freeze well, such as breast specimens. Microscopy with ultraviolet Surface Excitation (MUSE) is a nondestructive superficial optical-sectioning technique that has the potential to enable rapid, high-resolution examination of excised margin Surfaces. Here, a MUSE system is developed with fully automated sample translation to image fresh tissue Surfaces over large areas and at multiple levels of defocus, at a rate of ∼5 min / cm2. Surface extraction is used to improve the comprehensiveness of Surface imaging, and 3-D deconvolution is used to improve resolution and contrast. In addition, an improved fluorescent analog of conventional H&E staining is developed to label fresh tissues within ∼5 min for MUSE imaging. We compare the image quality of our MUSE system with both frozen-section and conventional H&E histology, demonstrating the feasibility to provide microscopic visualization of breast margin Surfaces at speeds that are relevant for intraoperative use.
Nicolas Pauly - One of the best experts on this subject based on the ideXlab platform.
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Surface Excitation parameter for allotropic forms of carbon
Surface and Interface Analysis, 2012Co-Authors: Nicolas Pauly, Mihaly Novak, Sven TougaardAbstract:The Surface Excitation parameter (SEP) is calculated for five carbon allotropes: amorphous carbon, graphite, glassy carbon, C60-fullerite and diamond for electron energies between 300 eV and 3400 eV, and for angles between 0° and 60° to the Surface normal. SEP, defined as the change in Excitation probability, for an electron, caused by the presence of the Surface in comparison with an electron moving the same distance in an infinite medium, is calculated within two dielectric response models due to Yubero and Tougaard (YT) and Tung, Chen, Kwei and Chou (TCKC) respectively. We show that SEP results obtained from TCKC are roughly independent of the allotrope while values calculated from YT are clearly material dependent. Moreover we find that SEP calculated from TCKC is on average 40% larger than those calculated from YT, the difference being largest for materials with large band gap energy. This difference is due to the simplified description of Surface Excitations in TCKC Copyright © 2012 John Wiley & Sons, Ltd.
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Comparison between Surface Excitation parameter obtained from QUEELS and SESINIPAC
Surface and Interface Analysis, 2012Co-Authors: Nicolas Pauly, Mihaly Novak, Alain Dubus, Sven TougaardAbstract:Surface Excitations significantly influence the measured peak intensities in elastic peak electron spectroscopy. They are characterised by the Surface Excitation parameter (SEP) defined as the change in Excitation probability of an electron caused by the presence of the Surface in comparison with an electron moving in an infinite medium. It is thus important to have a large database of SEP values or to have the possibility to determine it with a user-friendly software. Recently, Novak developed the programme Software for Electron Solid Inelastic Interaction Parameter Calculations (SESINIPAC) within the model of Tung, Chen, Kwei and Chou, which allows to determine inelastic mean free path, differential inelastic mean free path, SEP and differential SEP for various energy loss function models and dispersion relations with as only input the energy loss function of the material. Using SESINIPAC, we calculate SEP for 27 different types of materials (metals, semiconductors and insulators) and for various angles and energies. We compare these results with those obtained previously with the software Quantitative Analysis of Electron Energy Losses at Surfaces (QUEELS), which uses the Yubero-Tougaard model. We show that the dependence on angle of emission and energy is quite similar for the two models. However, the absolute values calculated with SESINIPAC are generally larger than those calculated with QUEELS, and the mean relative difference is 20% for metals and semiconductors but exceeds 50% for insulators. Copyright © 2012 John Wiley & Sons, Ltd.
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Core hole and Surface Excitation correction parameter for XPS peak intensities
Surface Science, 2011Co-Authors: Nicolas Pauly, Sven TougaardAbstract:Abstract In XPS analysis, Surface Excitations and Excitations originating from the static core hole created during the photoExcitation process are usually neglected. However, both effects significantly reduce the measured peak intensity. In this paper we have calculated these effects. Instead of considering the two effects separately, we introduce a new parameter, namely the Correction Parameter for XPS (or CPXPS) defined as the change in probability for emission of a photoelectron caused by the presence of the Surface and the core hole in comparison with the situation where the core hole is neglected and the electron travels the same distance in an infinite medium. The CPXPS calculations are performed within the dielectric response theory by means of the QUEELS-XPS software determining the energy-differential inelastic electron scattering cross-sections for X-ray photoelectron spectroscopy (XPS) including Surface and core hole effects. This study has been carried out for electron energies between 300 eV and 3400 eV, for angles to the Surface normal between 0° and 60° and for various materials, especially metals, semiconductors and oxides. For geometries and energies normally used in XPS, i.e. for emission angle ≤ 60° and photoelectron energy ≤ 1500 eV, we find that CPXPS values are significantly larger for oxides, (0.55 ≲ CPXPS ≲ 0.75) than for metals and semiconductors (0.45 ≲ CPXPS ≲ 0.6). We show that this behavior is due to the difference in the wave vector dispersion of the energy loss function. This dispersion has been determined from analysis of REELS and is found to be free electron like (α ≅ 1) for metals but is substantially smaller (α ≈ 0.02–0.05) for materials with a wide band gap. As a result, the group velocity of the valence electrons is very small for oxides with a large band gap. This leads to a reduction in the screening of the core-hole potential before the photoelectron has left the region of interaction and thereby to an increase in the intrinsic Excitations caused by the core hole.
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Surface Excitation parameter for 12 semiconductors and determination of a general predictive formula
Surface and Interface Analysis, 2009Co-Authors: Nicolas Pauly, Sven TougaardAbstract:The Surface Excitation parameter (SEP) is theoretically calculated for 12 semiconductors (GaN, GaP, GaSb, GaAs, InSb, InAs, InP, SiC, ZnSe, ZnS, Si and Ge) and for Ni (which is usually used as a reference in experiments) for electron energies between 300 eV and 3400 eV, and for angles between 0° and 70° to the Surface normal. We use our previous definition of SEP, as the change in Excitation probability, for an electron, caused by the presence of the Surface in comparison with an electron moving the same distance in an infinite medium. The calculations are performed within the dielectric response theory by means of the QUEELS-e(k, ω)-REELS software determining the energy-differential inelastic electron scattering cross-sections for reflection-electron-energy-loss spectroscopy (REELS), and for which the only input is the dielectric function of the medium. By fitting to these SEP values as well as our previous ones, i.e. from 27 materials, including metals, oxides, polymers and semiconductors, we also establish a simple equation depending on the generalized plasmon energy and the energy band gap of the material which allows to estimate the SEP when the dielectric function is not available. Copyright © 2009 John Wiley & Sons, Ltd.
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Calculation of the angular distribution of the Surface Excitation parameter for Ti, Fe, Cu, Pd, Ag and Au
Surface and Interface Analysis, 2008Co-Authors: Nicolas Pauly, Sven TougaardAbstract:We define Surface Excitation parameter (SEP) as the change in Excitation probability of an electron caused by the presence of the Surface in comparison with an infinite medium, and we calculate the angular dependence of the SEP for different metals (Ti, Fe, Cu, Pd, Ag, and Au), for angles to the Surface normal between 10° and 70° and for different energies. The calculations are based on a study of energy-differential inelastic electron scattering cross-sections obtained from the software Quantitative analysis of Electron Energy Losses at Surfaces (QUEELS) valid for reflection-electron-energy-loss spectroscopy (REELS). The intensity of the Surface Excitation is isolated from the total spectrum by subtracting the volume component for an infinite medium and the SEP is deduced from it. Copyright © 2008 John Wiley & Sons, Ltd.
