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Oscillator strengths for C 1s, N 1s, and O 1s excitation spectra of aniline, nitrobenzene, and the isomeric nitroanilines have been derived from inner-shell electron energy loss spectroscopy recorded under low momentum transfer conditions (> 2.5 keV impact energy and small scattering angle, θ ≤ 2°). Extended Hückel Molecular Orbital (EHMO) calculations carried out within the equivalent core analogy are used to aid spectral interpretation. These spectra are used to investigate the sensitivity of core excitation spectroscopy to charge transfer interactions in aromatic molecules that have both electron-donating and electron-withdrawing substituents. Strong multielectron excitation features were not found, although these had been anticipated from photoemission studies. The C 1s → π* and N 1s (NH2) → π* spectral features of the nitroanilines are found to be strongly dependent on the substitution pattern (ortho, meta, or para). Key words: electronic structure, inner-shell excitation, nitroanilines, EHMO calculations.

The Si 1s, Si 2s and Si 2p core-level photoabsorption spectra of hexamethyldisilane have been recorded by synchrotron radiation and calculated by the multiple-scattering (MS) X α method. The results of the calculation are in semiquantitative agreement with the experimental spectra. The relative intensity of corresponding transitions at the (1s, 2s) or (2p) edges differs greatly on account of atomic-like propensity rules (s → p, p → s, d). Comparison of the gas phase and solid state Si 2p spectra with the MS-X α results indicates that many of the features in the Si 2p spectrum of hexamethyldisilane correspond to transitions to states of mixed valence and Rydberg character.

Silicon 1s Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of silicon nanocrystals have been examined as a function of nanocrystal size (3-100 nm), varying surface functionalization (hydrogen or 1-pentyl termination), or embedded in oxide. The NEXAFS spectra are characterized as a function of nanocrystal size and surface functionalization. Clear spectroscopic evidence for long range order is observed silicon nanocrystals that are 5-8 nm in diameter or larger. Energy shifts in the silicon 1s NEXAFS spectra of covalently functionalized silicon nanocrystals with changing size are attributed to surface chemical shifts and not to quantum confinement effects.

The C 1s, N 1s, and O 1s excitation spectra of model methylenediphenyldiisocyanate (MDI) polyurethanes with well known structures have been recorded using electron energy loss spectroscopy (EELS) in an electron microscope. These spectra are compared to the core excitation spectra of selected small molecule analogue species (recorded by gas phase EELS) in order to identify transitions characteristic of various structural components found in polyurethanes. A more detailed report on the small molecule analogue spectra is presented in the following article. Spectral features characteristic of the different structural components in polyurethanes are identified in the spectra of the model polymers. These can be used as the basis for chemical studies of micron or submicron sized segregated phases in flexible polyurethane polymers. © 1995 John Wiley & Sons, Inc.

Core excitation spectra of selected small molecule analogue species have been acquired to assist interpretation of the core excitation spectra of model methylenediphenyldiisocyanate (MDI) polyurethane polymers. Oscillator strength spectra for C Is and O Is core excitation of diethyl ether and diisopropyl ether ; C Is, N Is, and O Is core excitation of urea, N-phenyl urea, N,N'-diphenyl urea, ethyl carbamate, N-phenyl carbamate, N-phenyl N-methyl carbamate, and benzyl carbamate have been derived from gas phase electron energy loss spectra (EELS). Extended Hiickel Molecular Orbital (EHMO) calculations are used to assist assignment and to interpret the effect of π-electron delocalization on the gas phase spectra. Functional group identification by core excitation is explored for the purpose of using core excitation spectra for microanalysis of polyurethane polymers. © 1995 John Wiley & Sons, Inc.

Upon adsorption on the (111) facet of Ag, 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid (PVBA) self-assembles into a highly ordered, chiral twin chain structure at submonolayer coverages with domains that can extend for micrometers in one dimension. Using polarization-dependent measurements of C and N K-shell excitations in near-edge X-ray absorption fine structure (NEXAFS) spectra, we determine the binding geometry of single PVBA molecules within this unique ensemble for both low and high coverage regimes. At submonolayer coverage, the molecule is twisted to facilitate the formation of hydrogen bonds. The gas-phase planarity is gradually recovered as the coverage is increased, with complete planarity coinciding with loss of order in the overlayer. Thermal treatment of the PVBA film results in deprotonation of the carboxyl tail of the molecule, but despite the suppression of the stabilizing hydrogen-bonds, the overlayer remains ordered.

Oscillator strengths for the Si 2p, Si 2s, and C 1s excitation of tetramethylsilane, hexamethyldisilane, tetrakis(trimethylsilyl)silane, and dodecamethylcyclohexasilane have been derived from electron energy loss spectra recorded in the dipole-regime. These results are compared to the Si l s and Si 2p photoabsorption spectra of tetramethylsilane, hexamethyldisilane, tris(trimethylsilyl)silane, and tetrakis(trimethylsilyl)silane, recorded using synchrotron radiation. The spectra support the existence of a localised, low-lying state of large Si-Si character in species which contain Si-Si bonds.

The Si 1s (K‐shell) x‐ray absorption spectra of several [(Si)m(Ge)n]p atomic layer superlattices (ALS) and a range of SixGe1−x alloy thin films grown epitaxially on both Si(100) and Ge(100) have been investigated using plane‐polarized synchrotron radiation. The near‐edge spectral features of ALS and alloy samples with similar (average) chemical composition are remarkably similar. The spectra of both the strained ALS and alloy samples contain features at the Si 1s threshold which exhibit a small but characteristic polarization dependence. The polarization dependence is reduced or absent in strain‐relaxed materials such as annealed ALS, annealed alloys, or thick alloy films. The polarization‐dependent components of the signal are attributed to anisotropic states associated with strain‐induced tetragonal distortions. The sense of the polarization is inverted between samples grown on Si and those grown on Ge, consistent with the expected inversion in the spatial orientation of the strain field. An explanation...

We have modified scanning transmission x‐ray microscopes (STXM) at the Canadian Light Source and the Advanced Light Source with total electron yield (TEY) detection (TEY‐STXM). This provides improved surface‐sensitive detection, simultaneous with existing bulk‐sensitive transmission detection in the STXM microscopes. We have explored sample‐current and channeltron‐based electron yield detection. Both approaches provide improved surface sensitive imaging and spectroscopy, although channeltron‐based detection is superior. TEY‐STXM provides surface sensitive imaging of ultrathin films such as phase‐separated Langmuir‐Blodgett monolayer films, as well as differentiation of surface and bulk oxides of patterned metallic thin films. This paper will outline the experimental challenges of this method and the opportunities for correlative surface and bulk measurements of complex samples.

The successful application of X-ray spectromicroscopy to chemical analysis of polymers is reviewed and a detailed application to quantitative analysis of polyurethanes is presented. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is the basis of chemical sensitive X-ray imaging, as well as qualitative and quantitative micro-spectroscopy. These capabilities are demonstrated by a review of recent work, and by presentation of new results outlining a methodology for quantitative speciation of polyurethane polymers. C 1s inner-shell excitation spectra of a series of molecular and polymeric model compounds, recorded by gas phase inelastic electron scattering (ISEELS) and solid phase NEXAFS techniques, are used to understand the spectroscopic basis for chemical analysis of polyurethanes. These model species contain the aromatic urea, aromatic urethane (carbamate) and aliphatic ether functionalities that are the main constituents of polyurethane polymers. Ab initio calculations of several of the model molecular compounds are used to support spectral assignments and give insight into the origin and relative intensities of characteristic spectral features. The model polymer spectra provide reference standards for qualitative identification and quantitative analysis of polyurethane polymers. The chemical compositions of three polyurethane test polymers with systematic variation in urea/urethane content are measured using the spectra of model toluene diisocyanate (TDI) urea, TDI-carbamate, and poly(propylene oxide) polymers as reference standards.

Oscillator strengths for C 1s and O 1s excitation of terephthalaldehyde, benzaldehyde, and ethyl benzoate and C 1s, O 1s and Cl 2p excitation of terephthaloyl chloride and phosgene have been derived from electron energy loss spectra recorded under scattering conditions where electric dipole transitions dominate. Extended Hueckel molecular orbital (EHMO) calculations were used to aid interpretation of the core excitation spectra of these multifunctional organic molecules. The experimental molecular spectra and EHMO calculations were used to estimate the C 1s and O 1s core excitation spectra of poly(ethylene terephthalate) (PET). Comparisons to the C 1s and O 1s energy loss spectra of PET recorded in an electron microscope have demonstrated that gas-phase spectra and theoretical studies of molecular analogues are useful in interpreting the core excitation spectra of polymers. 48 refs., 14 figs., 13 tabs.

We have recorded the iron 2p and carbon 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of decamethyl ferrocene (Fe 3d(6)) and ferrocenium hexafluorophosphate (Fe 3d(5)), two low spin compounds with closed- and open-shell electron configurations, respectively. These species have a similar covalent bonding environment but a different electron configuration, allowing us to examine the role of ligand-metal interactions and electron correlation responsible for their NEXAFS spectra. We have interpreted these spectra with the aid of ab initio configuration interaction (CI) calculations. The CI calculations indicate that double excitation is essential to interpret the Fe 2p NEXAFS spectra of not only the open-shell ferrocenium ion but also the closed-shell ferrocene species, even though the ground states of both species are well described within the Hartree-Fock single-configuration approximation.

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and microscopy has been used to study the orientational morphology of thin films of the linear alkanes n-C36H74 and n-C60H122, prepared by vacuum deposition onto NaCl (001) surfaces at ambient and elevated substrate temperatures. The orientational morphology, specifically, the nature of domains with lateral and normal orientation, is explored as a function of the chain length and the substrate temperature. It is found that the longer n-C60H122 molecules are laterally oriented on the substrate surface within the investigated substrate temperatures but that the morphology of these thin films varies with substrate temperature. The shorter n-C36H74 molecules are partially laterally oriented at low substrate temperature and are completely normally oriented at high substrate temperature. The relative magnitude of "side-by-side" and "end-to-end" intermolecular interactions leads to the formation of highly ordered alkane structures with a high aspect ratio. The formation of complex, nanoscale orientational morphologies are rationalized by considering kinetic and thermodynamic effects, in particular, the relative enthalpic and entropic contributions to the free energy associated with the different molecular orientations.

Considerable variation is observed in the near-edge X-ray absorption fine structure (NEXAFS) spectra of amino acids. To unambiguously characterize the chemical origin of this variation, we have acquired the nitrogen 1s NEXAFS spectra of several amino acids and other model compounds and complemented these experimental measurements with ab initio calculations of isolated molecules and molecular clusters. The systematic differences observed between the zwitterionic and un-ionized forms of amino acids arise directly from the structural difference (−NH2 vs −NH3+), which leads to a change in the degree of Rydberg−valence mixing. Further change arises from quenching of this Rydberg character in the spectra of condensed amino acids. Ab initio calculations are used to explore the degree of Rydberg−valence mixing in the solid state.

The carbon 1s near edge x-ray absorption fine structure (NEXAFS) spectra of simple gaseous alkane molecules differ from the spectra of the same alkane molecules in the condensed phase. The origin of these large, systematic differences is poorly understood. The NEXAFS spectra of gaseous alkanes are interpreted as a progression of core--Rydberg transitions with distinctive vibronic structure. The interpretation of the NEXAFS spectra of condensed phase alkanes is varied. Specifically, the degree of Rydberg character in the pre-edge core excited states of condensed alkanes is controversial. We determined the character of core excited states in condensed alkanes with a combination of experiment and computational study. From this, we have determined the nature of matrix effects for these species. The high-resolution carbon 1s NEXAFS spectrum of gaseous neopentane is dramatically different from its condensed phase spectrum, a striking illustration of the dramatic spectroscopic changes that occur upon condensation. High quality ab initio calculations of a cluster designed to model the solid phase environment provide definitive evidence for the reduction of Rydberg character and support the assignment of sigma*C-H) valence character in the pre-edge features in the NEXAFS spectra of condensed alkanes.

The nature of the linear dichroism in the near-edge X-ray absorption fine structure (NEXAFS) spectra of linear n-alkanes is a matter of long-standing controversy. Linear dichroism in the carbon 1s --> sigma*(C-C) transition has been interpreted within a building block model and a molecular orbital model, leading to two different descriptions for the angular dependence of this feature. When used for measurement of molecular orientation, the application of these two different models will lead to different results. We have explored the linear dichroism in the carbon 1s NEXAFS spectra of single crystals of the linear n-alkane hexacontane (n-C60H122). An analysis of the angular dependence in this spectrum shows that the transition dipole moment associated with the carbon 1s --> sigma*(C-C) transition is oriented along the macromolecular chain axis, contradicting the predictions of the building block model. However, other transitions are observed in the sigma*(C-H) and the sigma*(C-C) bands that are orthogonal to the dominant transitions for each band. We also observe that radiation damage can be manifest in the form of molecular reorientation in highly ordered organic thin films.

We report on a high-resolution C–K and O–K near-edge x-ray-absorption fine-structure (NEXAFS) study of large aromatic molecules in condensed thin films, namely, anhydrides 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride, 3,4,9,10-perylene-tetracarboxylic acid dianhydride, benzoperylene-(1,2)-dicarboxylic acid anhydride, and 1,8-naphthalene-dicarboxylic acid anhydride and the quinoic acenaphthenequinone. Due to the high-energy resolution of the third-generation synchrotron source BESSY II we observe large differences in the NEXAFS fine structures even for very similar molecules, resulting in a wealth of new information. The rich fine structure can unambiguously be assigned to the coupling of electronic transitions to vibronic excitations. Backed by ab initio calculations we present a detailed analysis of the spectra that allows the complete interpretation of the near-edge features. It also yields information on the vibronic properties in the electronically excited state as well as on the response of the electronic system upon core excitation. The strong differences in the electron-vibron coupling for different molecules are discussed.

We report additional rich fine structures in high-resolution near-edge x-ray-absorption fine structure (NEXAFS) spectra of large organic molecules using NTCDA on Ag(111) as an example. These fine structures are completely interpreted as vibronic coupling to electronic core excitations. The coupling is mode selective; predominantly one vibronic mode couples to each excitation. The fit results suggest the occurrence of a Davydov splitting, first observed for core excitons. Morphological differences substantially influence the electron-vibron coupling, indicating a strong intermolecular interaction. Thus NEXAFS becomes a more subtle probe for organic solids.

The spectromicroscopy beamline (SM) at the Canadian Light Source (CLS) will provide 100 – 2000 eV photons in a high brightness, high flux, medium resolution and small spot size beam. The beamline consists of an advanced elliptically polarized undulator (EPU) source and a novel entrance slit‐less plane grating monochromator which feeds two branch lines, one optimized for scanning transmission X‐ray microscopy (STXM), the other for X‐ray photoemission electron microscopy (X‐PEEM). This article outlines the beamline design strategy, and discusses the design optimization relative to the requirements for state‐of‐the‐art STXM and X‐PEEM.

UVX2010, the 37th International Conference on Vacuum Ultraviolet and X-ray Physics, took place from July 11-16, 2010, on the campus of the University of British Columbia (UBC). This meeting was the first of the merged Vacuum Ultraviolet Radiation Physics and X-ray and Inner Shell Processes conference series. The immediate preceding conferences were VUV15 (Berlin, 2007), and X-08 (Paris, 2008). VUVX2010 brought together scientists from countries all over the world working with synchrotron-, laser-, and plasma-based sources of electromagnetic radiation in the vacuum ultraviolet (VUV), soft X-ray, and hard X-ray regions, and developing novel applications of these sources in a variety of fields. Topics presented ranged from basic physics to materials science and technology, from molecular reactions to the characterization of catalysts under working conditions, from biology to medical diagnostics, from metrology to the development of advanced synchrotron and optical instrumentation. There were over 500 oral an...

The morphology, size distributions, spatial distributions, and quantitative chemical compositions of co-polymer polyol-reinforcing particles in a polyurethane have been investigatedwith scanning transmission X-ray microscopy (STXM). A detailed discussion of microscope operating procedures is presented and ways to avoid potential artifacts are discussed. Images at selected photon energies in the C 1s, N 1s and O 1s regions allow unambiguous identification of styrene–acrylonitrile-based (SAN) copolymer and polyisocyanate polyaddition product-based (PIPA) reinforcing particles down to particle sizes at the limit of the spatial resolution (50 nm). Quantitative analysis of the chemical composition of individual reinforcing particles is achieved by fitting C 1s spectra to linear combinations of reference spectra. Regression analyses of sequences of images recorded through the chemically sensitive ranges of the C 1s, N 1s andO 1s spectra are usedto generate quantitative compositional maps, which provid e a fast andeffective means of investigating compositional distributions over a large number of reinforcing particles. The size distribution of all particles determined by STXM is shown to be similar to that determined by TEM. The size distributions of each type of reinforcing particle, which differ considerably, were obtained by analysis of STXM images at chemically selective energies. # 2001 Elsevier Science B.V. All rights reserved.

Thiophenic compounds are major constituents of fossil fuels and pose problems for fuel refinement. The quantification and speciation of these compounds is of great interest in different areas such as biology, fossil fuels studies, geology, and archaeology. Sulfur 1s Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy has emerged as a qualitative and quantitative method for sulfur speciation. A firm understanding of the sulfur 1s NEXAFS spectra of organosulfur species is required for these analytical studies. To support this development, the sulfur 1s NEXAFS spectra of simple thiols and thioethers were previously examined, and are now extended to studies of thiophenic and aromatic thioether compounds, in the gas and condensed phases. High-resolution spectra have been further analyzed with the aid of Improved Virtual Orbital (IVO) and Δ(self-consistent field) ab initio calculations. Experimental sulfur 1s NEXAFS spectra show fine features predicted by calculation, and the combination of experiment and calculation has been used to improve the assignment of spectroscopic features important for the speciation and quantification of sulfur compounds. Systematic differences between gas and condensed phases are also explored; these differences suggest a significant role for conformational effects in the NEXAFS spectra of condensed species.

Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy of polymers performed in a scanning transmission X-ray microscope (STXM) can provide chemical speciation with

We present high resolution oxygen K near-edge x-ray absorption spectra of the acenaphthenequinone (ANQ) derivative 3,8-dibromo-5,6-dichloro-ANQ (Br(2)Cl(2)-ANQ). The spectral features exhibit an almost identical vibronic fine structure compared to that shown by ANQ. The unequal distances of the vibronic levels as derived from the least-squares fit analysis of the vibronic progressions allows us to determine the anharmonicity of the excited state potentials involved. We conclude that a single vibrational progression couples to the resonant excitation of O 1s core electrons preferentially. Comparison of the two ANQ derivatives gives a clear indication that the vibronic mode corresponds to a C=O stretching mode, rather than coupling to a C-H mode as suggested previously. These conclusions are supported by density functional theory calculations.

The narrow energy band pass of an energy-filtered x-ray photoemission electron microscope (X-PEEM) can lead to unusual artifacts when used for spatially resolved near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and imaging of organic surfaces. Work-function differences and the rapid work-function change with radiation exposure can impair quantitative chemical analysis by NEXAFS and invert the expected image contrast. We also find that "partial-yield" detection from the narrow energy band pass of an energy-filtered X-PEEM can lead to distorted NEXAFS spectra. These observations not only are relevant for the analysis of organic surfaces by energy-filtered X-PEEM but also call into question some assumptions about quantitative NEXAFS spectroscopy.

The speciation and quantification of sulfur species based on sulfur K-edge x-ray absorption spectroscopy is of wide interest, particularly for biological and petroleum science. These tasks require a firm understanding of the sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of relevant species. To this end, we have examined the gas phase sulfur 1s NEXAFS spectra of a group of simple thiol and thioether compounds. These high-resolution gas phase spectra are free of solid-state broadening, charging, and saturation effects common in the NEXAFS spectra of solids. These experimental data have been further analyzed with the aid of improved virtual orbital Hartree-Fock ab initio calculations. The experimental sulfur 1s NEXAFS spectra show fine features predicted by calculation, and the combination of experiment and calculation has been used to improve assignment of spectroscopic features relevant for the speciation and quantification of the sulfur compounds.

Ge islands with areas up to hundreds of μm2 were grown on Si(111). These islands, grown above 750 °C and at a deposition rate of 1 monolayer/min, become decreasingly compact with increasing size and can have nonuniform cross sections with heights reaching over 500 nm. The largest islands are ramified, often comprising multiple discrete parts. X-rayphotoemission electron microscopy absorption maps show that the islands have a higher concentration of Ge at their centers, with more Si near the edges. We propose that the shape transformation is driven by strain relief at the island perimeters.

Soft X-ray spectromicroscopy is emerging as a powerful method for the chemical and structural analysis of nanostructured organic materials. X-ray spectromicroscopy combines the chemical and structural sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy with the high spatial resolution of X-ray microscopy. Linear Dichroism (LD), the anisotropic absorption of linearly polarised radiation by an oriented molecule, is observed in NEXAFS spectra. LD-NEXAFS offers excellent sensitivity to molecular orientation, and can be used to characterise molecular order in materials at high spatial resolution. Technical developments in X-ray microscopy and synchrotron undulator sources have enhanced X-ray Linear Dichroism Microscopy (XLDM) studies of organic materials. This paper will review the state of XLDM for studies of oriented organic materials, its relationship to other techniques, and the prospects for the study of nanoscale organic materials with new spectromicroscopy facilities, such as those at the Canadian Light Source.

We use the Scanning Transmission X-ray Microscope (STXM) at the National Synchrotron Light Source (NSLS) (1) to acquire images and spectra of polymers. To interpret data correctly, the effects X-ray radiation has on polymers must be understood. We have therefore started to characterize radiation damage in a variety of carbonyl containing polymers in two ways. First, we want to ascertain the critical dose for mass loss and the critical dose for the carbonyl in a variety of polymers and relate the critical dose to the polymer structure. (The critical dose is the radiation dose at which the optical density of the material is decreased by 1/e of its original value.) We also want to understand the damage mechanism. STXM acquires images and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra by using X-ray photons to excite inner shell electrons to unoccupied valence orbitals or to the continuum.

Phase segregation is important in determining the properties of many complex polymers, including polyurethanes. Achieving a better understanding of the links between formulation, chemical nature of segregated phases, and physical properties, has the potential to aid development of improved polymers. However, the sub-micron size of segregated features precludes detailed chemical analysis by most existing methods. Zone-plate based, scanning transmission X-ray microscopes (STXM) at NSLS and ALS provide quantitative chemical analysis (speciation) of segregated polymer phases at ∼50 nm spatial resolution. Image sequences acquire much more data with less radiation damage, than spot spectra. After alignment, they provide high quality near edge spectra, and thus quantitative analysis, at full spatial resolution.Fig. 1 shows an image and spectra acquired with the NSLS STXM of a macro-phase segregated TDI polyurethane. Spectral decomposition using model polymer spectra is used to measure the local urea, urethane and polyether content.

Superabsorbent polymers are often designed with increased density of crosslinking in the outer layer of the particles in order to improve liquid retention under load. For efficient product design, it is desirable to directly measure the spatial variation in crosslink density. Typically employed techniques (such as solvent uptake or measuring the changes in various mechanical properties such as the modulus) do not provide spatially resolved crosslink density information. We have applied Scanning Transmission X-ray Microscopy to examine the swelling of inhomogenously crosslinked superabsorbent polymers in deionized water and salt water solution.Scanning Transmission X-ray Microscopy (STXM) is an effective way to study the chemical and morphological character of polymers on a sub micron spatial scale.1 STXM image contrast is based on core electron excitation by x-ray absorption; an interaction that has remarkable chemical sensitivity. Beam damage is less than in TEM microscopes and samples can be examined in wet and in ambient conditions.

Phase segregation is important in determining the physical and chemical properties of many complex polymers, including polyurethanes. Achieving a better understanding of the connections between formulation chemistry, the chemical nature of segregated phases, and the physical properties of the resulting polymer, has the potential to greatly advance the development of improved polyurethane materials. However, the sub-micron size of segregated features precludes their chemical analysis by most existing methods. Near edge X-ray absorption spectroscopy carried out with sub micron spatial resolution provides one of the few suitable means for quantitative chemical analysis (speciation) of individual segregated phases. We have used the NSLS and ALS scanning transmission x-ray microscopes (STXM) to record images and spectra of both model and real polyurethane polymers. Relative to energy loss spectroscopy in a transmission electron microscope, STXM has remarkable advantages with regard to a much lower radiation damage rates and much higher spectral resolution (∼0.1 eV at the C ls edge), with a spatial resolution (∼0.1 μm) adequate for many real world problems in polymer analysis.

The near-edge region of core ionization edges can be used as a probe of the local bonding and structure of atoms excited by incident radiation, such as in electron energy loss spectroscopy (EELS) or x-ray absorption techniques. Recent installation of efficient parallel EELS spectrometers in ATEMs promotes study of these transitions in radiation sensitive materials such as polymers. To study relationships between poly(ethylene terephthalate) [PET] structure and EELS transitions, we compared polymer spectra with molecular analogues.The PET examined (from Scientific Polymer Products) was cut using a diamond knife and a Reichert-Jung Ultracut E ultramicrotome with FC4E cryoattachment. A JEOL 2000FX TEM with a LaB6 filament and a Gatan parallel-EELS system was used to examine PET sections on holey carbon. The gas phase EELS of molecules (from Aldrich, Matheson) was performed under inelastic scattering conditions as described previously.

Oscillator strength spectra in the region of B 1s and C 1s excitation of three isomeric carborane cage compounds [closo-1,2-orthocarborane, closo-1,7-metacarborane, closo-1,12-paracarborane (C2B10H...