Showing papers on "Absorption spectroscopy published in 2001"
TL;DR: The lowest electronic absorption bands become increasingly intensified and red-shifted upon the increase in the number of porphyrins and eventually reach a peak electronic excitation for the dodecamer at ∼3500 wavenumber.
Abstract: Scandium(III)-catalyzed oxidation of meso-meso– linked zinc(II)-porphyrin arrays (up to dodecamers) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) led to efficient formation of triply meso-meso –, β-β–, and β-β–linked zinc(II)-oligoiporphyrins with 62 to 91% yields. These fused tape-shaped porphyrin arrays display extremely red-shifted absorption bands that reflect extensively π-conjugated electronic systems and a low excitation gap. The lowest electronic absorption bands become increasingly intensified and red-shifted upon the increase in the number of porphyrins and eventually reach a peak electronic excitation for the dodecamer at ∼3500 wavenumber. The one-electron oxidation potentials also decreased progressively upon the increase in the number of porphyrins. These properties in long and rigid molecular shapes suggest their potential use as molecular wires.
843 citations
TL;DR: In this paper, a review of high-resolution X-ray emission and Xray absorption spectroscopy is presented, where the focus is on the 3D transition-metal systems.
Abstract: In this review, high-resolution X-ray emission and X-ray absorption spectroscopy will be discussed. The focus is on the 3d transition-metal systems. To understand high-resolution X-ray emission and reso-nant X-ray emission, it is first necessary to spend some time discussing the X-ray absorption process. Section II discusses 1s X-ray absorption, i.e., the K edges, and section III deals with 2p X-ray absorption, the L edges. X-ray emission is discussed in, respectively, the L edges. X-ray emission is discussed in, respec-tively, and section V on 2p3s and 2p3d X-ray emission. Section VI focuses on magnetic dichroism effects, and in section VII selective X-ray absorption experiments are discussed. To limit the scope of this review paper, many related topics (for example, EELS, XPS, and resonant photoemission, phonon-oriented inelastic X-ray scat-tering, and X-ray microscopy) will not be discussed. In addition, many aspects of X-ray absorption, such as reflection experiments, diffraction absorption fine structure, and related experiments, will remain untouched. EXAFS will be discussed very briefly, and its X-ray emission analogue EXEFS 69,71 will not be discussed.
700 citations
TL;DR: In this article, a new photocatalyst (WOx-TiO2) powder was prepared by a sol-gel method by extending light absorption of the TiO2-based photocatalysts toward the visible light range and eliminating the rapid recombination of excited electrons/holes during photoreaction.
Abstract: With an attempt to extend light absorption of the TiO2-based photocatalysts toward the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, new photocatalyst (WOx-TiO2) powder was prepared by a sol–gel method. The photooxidation efficiency of WOx-TiO2 catalyst was also evaluated by conducting a set of experiments to photodegrade methylene blue (MB) in aqueous solution. The photocatalytic activity of WOx-TiO2 was examined by X-ray diffraction (XRD), UV–VIS absorption spectra, X-ray photoelectron emission spectroscopy (XPS), photoluminescence spectra (PL), surface photovoltage spectra (SPS) and electron-field-induced surface photovoltage spectra (EFISPS). The experiments demonstrated that the MB in aqueous solution was successfully photodegraded using WOx-TiO2 under visible light irradiation. It was found that an optimal WOx dosage of 3% in WOx-TiO2 achieved the highest rate of MB photodegradation in this experimental condition. It has been confirmed that WOx-TiO2 could be excited by visible light (E
672 citations
TL;DR: In this paper, a new type of photocatalysts (Au/Au3+-TiO2) powder was prepared by a photoreduction/sol−gel process.
Abstract: With an attempt to extend light absorption of TiO2-based photocatalyst toward the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, a new type of photocatalysts (Au/Au3+-TiO2) powder was prepared by a photoreduction/sol−gel process. The crystal phase composition, surface structure, and light absorption of the new photocatalysts were comprehensively examined by X-ray differential detection (XRD), UV−visible absorption spectra, X-ray photoelectron emission spectroscopy (XPS), and photoluminescence (PL) spectra. The photooxidation efficiencies of the photocatalysts were also evaluated in the photodegradation of methylene blue (MB) in aqueous solutions under visible light irradiation from a high-pressure sodium lamp (λ > 400 nm). The results of PL analyses in this study indicated that the gold/gold ion-doping on the surface of TiO2 could eliminate the electron/holes recombination and also increase the light absorption in the visible range. The analytica...
643 citations
TL;DR: In this article, the use of several analytical techniques, including X-ray absorption spectroscopy (XAS), electron microscopy, and electron diffraction, as tools for characterizing the structural dynamics of supported Pt nanoscale particles was described.
Abstract: In this report, we describe the use of several analytical techniques, including X-ray absorption spectroscopy (XAS), electron microscopy, and electron diffraction, as tools for characterizing the structural dynamics of supported Pt nanoscale particles. We examined several carbon-supported samples. Electron microscopy shows that the particles in these samples (S1−S3) have average particle diameters of roughly 20, 40, and 60 A respectively, while electron microdiffraction data for these particles provided evidence of long-ranged ordering in the form of face centered cubic structures. This study highlights the use of advanced synchrotron X-ray absorption spectroscopies (XAS), in particular extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES), as powerful tools for studying the structural habits and dynamics of these prototypical nanoscale materials. Using state-of-the-art methods of measurement and computational modeling, we demonstrate that it is possible to deve...
602 citations
TL;DR: In this article, high-resolution L-edge x-ray absorption spectroscopy (XAS) was used to investigate the interface of antiferromagnetic oxides with ferromagnetic metals.
Abstract: A chemical and magnetic characterization of ferromagnet/antiferromagnet interfaces is essential to understand the microscopic origins of exchange anisotropy and other magnetic phenomena. We have used high-resolution L-edge x-ray absorption spectroscopy (XAS), which is element specific and sensitive to chemical environment and spin orientation, to investigate the interface of antiferromagnetic oxides with ferromagnetic metals. Clear quantitative evidence of oxidation/reduction reactions at the as-grown metal/oxide interface is presented. In situ-- and ex situ--grown samples of the form oxide $(5--30 \AA{})/\mathrm{metal}$ $(1--10 \AA{}),$ where oxide is either NiO or CoO and metal is either Fe, Co, or Ni, were studied by high-resolution XAS. For all samples, a metal(oxide) layer adjacent to an oxide(metal) layer was partially oxidized(reduced). Quantitative analysis of the spectra showed that one to two atomic layers on either side of the interface were oxidized/reduced. An elemental series of samples showed that the amount of oxidation/reduction was in accord with the difference in oxidation potentials of the adjacent cations, e.g., oxide layers were more strongly reduced by an iron metal layer than by cobalt or nickel metal layers. Annealing to temperatures, typically used to bias devices, was shown to significantly increase the amount of oxidation/reduction. The oxidation behavior of iron was shown to depend on the amount of oxygen available. Our results are believed to provide important information for the improved understanding of exchange anisotropy.
520 citations
TL;DR: In this paper, specific binding of biotinilated bovine serum albumin (bBSA) and tetramethylrhodamine-labeled streptavidin (SAv−TMR) was observed by conjugating bBSA to CdSe−ZnS core−shell quantum dots (QDs) and observing enhanced TMR fluorescence caused by fluorescence resonance energy transfer (FRET) from the QD donors to the TMR acceptors.
Abstract: Specific binding of biotinilated bovine serum albumin (bBSA) and tetramethylrhodamine-labeled streptavidin (SAv−TMR) was observed by conjugating bBSA to CdSe−ZnS core−shell quantum dots (QDs) and observing enhanced TMR fluorescence caused by fluorescence resonance energy transfer (FRET) from the QD donors to the TMR acceptors. Because of the broad absorption spectrum of the QDs, efficient donor excitation could occur at a wavelength that was well resolved from the absorption spectrum of the acceptor, thereby minimizing direct acceptor excitation. Appreciable overlap of the donor emission and acceptor absorption spectra was achieved by size-tuning the QD emission spectrum into resonance with the acceptor absorption spectrum, and cross-talk between the donor and acceptor emission was minimized because of the narrow, symmetrically shaped QD emission spectrum. Evidence for an additional, nonspecific QD−TMR energy transfer mechanism that caused quenching of the QD emission without a corresponding TMR fluoresce...
484 citations
TL;DR: A photonic device based on a high-finesse, whispering-gallery-mode disk resonator that can be used for the detection of biological pathogens and formulas are presented that allow the sensitivity of the device to be quantified and that show that, under optimum conditions, as few as 100 molecules can be detected.
Abstract: We describe a photonic device based on a high-finesse, whispering-gallery-mode disk resonator that can be used for the detection of biological pathogens. This device operates by means of monitoring the change in transfer characteristics of the disk resonator when biological materials fall onto its active area. High sensitivity is achieved because the light wave interacts many times with each pathogen as a consequence of the resonant recirculation of light within the disk structure. Specificity of the detected substance can be achieved when a layer of antibodies or other binding material is deposited onto the active area of the resonator. Formulas are presented that allow the sensitivity of the device to be quantified and that show that, under optimum conditions, as few as 100 molecules can be detected.
451 citations
TL;DR: This method introduces a single-mode continuous-wave laser into the cavity by use of an off-axis cavity alignment geometry to eliminate systematically the resonances commonly associated with optical cavities, while preserving the absorption signal amplifying properties of such cavities.
Abstract: A simple and easy to use method that allows high-finesse optical cavities to be used as absorption cells for spectroscopic purposes is presented. This method introduces a single-mode continuous-wave laser into the cavity by use of an off-axis cavity alignment geometry to eliminate systematically the resonances commonly associated with optical cavities, while preserving the absorption signal amplifying properties of such cavities. This considerably reduces the complexity of the apparatus compared with other high-resolution cavity-based absorption methods. Application of this technique in conjunction with either cavity ringdown spectroscopy or integrated cavity output spectroscopy produced absorption sensitivities of 1.5 x 10(-9) cm(-1) Hz(-1/2) and 1.8 x 10(-10) cm(-1) Hz(-1/2), respectively.
339 citations
TL;DR: In this paper, a broadening of the 2.1-μm absorption feature is observed as nitrogen concentration increases and the wavelength positions of these absorptions coincide with the absorption characteristics of the nitrogen-containing amide bonds in proteins.
330 citations
TL;DR: The XAFS measurements confirm that photoexcitation leads to the rapid removal of both axial ligands to produce a transient square-planar intermediate, NiTPP, with a lifetime of 28 nanoseconds, suggesting that the intermediate adopts the same structure as the ground state in a noncoordinating solvent before it recombines with two ligand to form the more stable octahedrally coordinated NiTPP-L2.
Abstract: The determination of the structure of transient molecules, such as photoexcited states, in disordered media (such as in solution) usually requires methods with high temporal resolution. The transient molecular structure of a reaction intermediate produced by photoexcitation of NiTPP-L2 (NiTPP, nickeltetraphenylporphyrin; L, piperidine) in solution was determined by x-ray absorption fine structure (XAFS) data obtained on a 14-nanosecond time scale from a third-generation synchrotron source. The XAFS measurements confirm that photoexcitation leads to the rapid removal of both axial ligands to produce a transient square-planar intermediate, NiTPP, with a lifetime of 28 nanoseconds. The transient structure of the photodissociated intermediate is nearly identical to that of the ground state NiTPP, suggesting that the intermediate adopts the same structure as the ground state in a noncoordinating solvent before it recombines with two ligands to form the more stable octahedrally coordinated NiTPP-L2.
TL;DR: The measured absorption spectra agreed well with the ab initio calculations of band structure based on the local density function approximation, and the absorption bands are assigned to the dipole transitions between the Van Hove singularities.
Abstract: We report the polarized optical absorption spectra of single-walled $4\AA{}$ carbon nanotubes arrayed in the channels of an $\mathrm{AlPO}{}_{4}\ensuremath{-}5$ single crystal. When the light electric field $(E)$ is polarized parallel to the tube direction $(c)$, the spectra display a sharp peak at 1.37 eV, with two broadbands at 2.1 and 3.1 eV. In the $E\ensuremath{\perp}c$ configuration, the tube is nearly transparent in the measured energy region 0.5--4.1 eV. The optical dipole selection rules are discussed, and the absorption bands are assigned to the dipole transitions between the Van Hove singularities. The measured absorption spectra agreed well with the ab initio calculations of band structure based on the local density function approximation.
TL;DR: A polyaniline film was deposited on polyethylene surface by chemical oxidation of aniline monomer at room temperature, and the absorption spectra of the film was observed after it was exposed to ammonia gas.
Abstract: A polyaniline film was deposited on polyethylene surface by chemical oxidation of aniline monomer at room temperature. The ammonia gas sensing capabilities of the polyaniline film were studied using absorption spectroscopy method. A significant change was observed in the absorption spectra of the film after it was exposed to ammonia gas. The optical ammonia gas sensors have a response time of less than 15 s and a fast regeneration time of less than 2 min at room temperature. The sensors have a detection limit of 1 ppm (v/v) for ammonia, with a linear dynamic range from 180 to 18 000 ppm.
TL;DR: In this paper, high resolution, vibrationally resolved, near-edge x-ray absorption fine structure (NEXAFS) spectra at the C 1 s and N 1 s ionization thresholds of pyridine and deuterated d5-pyridine in the gas phase have been recorded.
Abstract: High resolution, vibrationally resolved, near-edge x-ray absorption fine structure (NEXAFS) spectra at the C 1s and N 1s ionization thresholds of pyridine and deuterated d5-pyridine in the gas phase have been recorded. The high resolution of 65 meV (150 meV) at the C s (N 1s) ionization thresholds reveals vibrational structures in the spectra. Detailed ab initio and density functional theory (DFT) calculations were performed to interpret the experimental spectra and to assign the observed peaks. In particular we focused on the previously unexplained intensity ratio for the two components of the C 1s→1π* transition. For this transition the vibrational structure is included through a linear coupling model in the DFT calculations and leads to the experimentally observed ∼2:3 intensity ratio between the two π* components in the C 1s spectrum rather than the ∼3:2 ratio obtained without vibrational effects. After inclusion of relaxation effects in the excited states, in addition to the vibrational effects, both theoretical methods yield almost perfect agreement with experiment.
TL;DR: It is shown that the anion form of the chromophore of the green fluorescent protein in vacuo has an absorption maximum at 479 nm, which coincides with one of the two absorption peaks of the protein.
Abstract: A sensitive photoabsorption technique for studies of gas-phase biomolecules has been used at the ELISA electrostatic heavy-ion storage ring. We show that the anion form of the chromophore of the green fluorescent protein in vacuo has an absorption maximum at 479 nm, which coincides with one of the two absorption peaks of the protein. Its absorption characteristics are therefore ascribed to intrinsic chemical properties of the chromophore. Evidently, the special beta-can structure of the protein provides shielding of the chromophore from the surroundings without significantly changing the electronic structure of the chromophore through interactions with amino acid side chains.
TL;DR: In this article, the authors have reviewed recent progress in the spectroscopic characterization of aliphatic and aromatic thiol-derived self-assembled monolayers (SAMs) on noble metal substrates.
Abstract: This article reviews recent progress in the spectroscopic characterization of aliphatic and aromatic thiol-derived self-assembled monolayers (SAMs) on noble metal substrates. Several complementary techniques such as near edge x-ray absorption fine structure spectroscopy, x-ray photoelectron spectroscopy, and infrared reflection absorption spectroscopy were applied to study the balance between intermolecular and adsorbate-substrate interactions, chemical identity of the headgroup, and absorption site homogeneity at the sulphur-metal interface. Whereas in the thioaliphatic SAMs the headgroup-substrate interaction was found to be a decisive factor for the structure and packing in these films, these parameters are mainly determined by the intermolecular interactions in the thioaromatic films. Only one sulphur species could be detected in the S 2p HRXPS spectra of both aliphatic and aromatic SAMs suggesting binding of individual molecules as thiolates. Conclusions on the heterogeneity of the adsorption sites are derived and evidence that the investigated films represent highly correlated molecular assemblies are presented.
TL;DR: A combination of in situ synchrotron X-ray diffraction (XRD) and Xray absorption spectroscopy (XAS) was used to study a two-electrode lithium-ion cell made from electrodes from a high-rate lithium ion battery as discussed by the authors.
TL;DR: In this paper, absolute absorption cross sections of O3 were measured in the 230 −850 nm region at five different temperatures (203 −293 K) using a Fourier-transform spectrometer, at a spectral resolution of 5.0 −1.
Abstract: Absolute absorption cross sections of O3 were measured in the 230–850 nm (11765–43478 cm−1) region at five different temperatures (203–293 K) using a Fourier-transform spectrometer, at a spectral resolution of 5.0 cm−1 (corresponding to about 0.027 nm at 230 nm and to about 0.36 nm at 850 nm). The spectral accuracy of the data is better than 0.1 cm−1 — about 0.5 pm at 230 nm and about 7.2 pm at 850 nm — validated by recording of I2 absorption spectra in the visible using the same experimental set-up. O3 absorption spectra at different concentrations were recorded at five different sample temperatures in the range 203–293 K, and at each temperature at two total pressures (100 and 1000 mbar) using O2/N2 mixtures as buffer gas. Within the limits of experimental uncertainties, no influence of total pressure on the O3 spectrum was observed in the entire spectral region, as expected from the short lifetimes of the upper electronic states of O3. The temperature dependence of the O3 absorption cross sections is particularly strong in the Huggins bands between 310 and 380 nm, as observed in previous studies. An empirical formula is used to model the temperature dependence of the O3 absorption cross sections between 236 and 362 nm, a spectral region that is particularly important for atmospheric remote-sensing and for photochemical modelling.
TL;DR: In this article, fine polycrystalline, nanoparticles of pure anatase titanium dioxide (average crystallite size ∼3-10 nm) with high surface area (∼210 m2/g) have been synthesized in the pure titanium phase, and the prepared nanoparticles showed a blue shift in the absorption spectra.
TL;DR: In this article, absorption and emission spectra for Yb3+-doped Y 2 O 3, Lu 2O 3 and Gd2O3 at room temperature are given.
TL;DR: In this paper, the adsorption of short 16 base pair DNA to 14 nm protein-sized gold particles using surface-enhanced Raman spectroscopy and electronic absorption spectrographs was examined.
Abstract: We have examined the adsorption of short 16 base pair DNA to 14 nm protein-sized gold particles using surface-enhanced Raman spectroscopy and electronic absorption spectroscopy. In the presence of KCl, we find greater Raman enhancement of adenine and guanine ring breathing vibrations (per adenine and guanine present in each sequence) for crystallographically “kinked” oligonucleotide than for the DNA−particle interactions for “bent” A-tract and “straight” oligonucleotides. The calculated binding constants are within the range of nonspecific protein−DNA interactions and are nearly the same for each sequence. The difference in the surface plasmon frequency of the gold particles in the presence of either straight, bent, or kinked DNA is attributed to differences in the DNA-mediated aggregation of the nanoparticles. Specifically, the displacement of the gold's stabilizing citrate ions seems to vary with DNA sequence, and this controls the residual interparticle electrostatic interaction and average interpartic...
Journal Article•
TL;DR: In this paper, the authors measured the absorption spectrum of bovine skin gelatin and elastin in hog eye lens as references of protein and found that temperature has a strong effect on the absorption property of water but not on fatty acid mixture.
Abstract: Near infrared (NIR) can penetrate relatively deep into biological soft tissues. The NIR absorption property of tissue varies with tissue constituents especially water, fat, collagen, and their combination ratio. Therefore, combination ratio of tissue constituents can be evaluated by decomposing the absorption spectrum to determine the light path length in each constituent. Standardized absorption spectra of tissue constituents are required in order to carry out decomposition. Since water, fat, and protein are the major contributors at NIR spectral region. This study is to measure their absorption spectra from standardized samples as reference for quantifying tissue constituents. Five kinds of major fatty acid found in human fat were mixed in proper ratio as a standard reference. Absorption spectrum of bovine skin gelatin and elastin in hog eye lens were used as references of protein. NIR absorption spectra were measured using a Shimadzu 3101-PC spectrophotometer. The results show that temperature has a strong effect on the absorption property of water but not on fatty acid mixture. Absorption spectrum of elastin is similar to that of dry bovine gelatin. NIR spectroscopy also can be used to characterize or identify different types of soft tissue based on their major chemical composition, such as detecting a fat plaque in a muscular tissue or a tumor in a high fat content tissue.
TL;DR: In this paper, the optical properties of small colloidal InP quantum dots with diameters ranging from 15 to 23 A were studied, and the absorption spectra of close-packed solids of ∼18 A diameter QDs with interdot spacings of 9 and 18 A showed that the absorption onsets and excitonic peaks are, respectively, redshifted and broadened in going from dilute solution to close packed solids.
Abstract: Extremely small colloidal InP quantum dots (QDs) with diameters ranging from 15 to 23 A were synthesized, and the optical properties of close-packed arrays of these dots were studied. The isolated QDs in dilute colloidal solution exhibit pronounced discrete absorption spectra, indicating a narrow size distribution. The absorption spectra of close-packed solids of ∼18 A diameter QDs with interdot spacings of 9 and 18 A show that the absorption onsets and excitonic peaks are, respectively, redshifted and broadened in going from dilute solution to close-packed solids. These results can be explained by electron delocalization in disordered close-packed solids; the spacing of electronic levels in the QDs is reduced and produces a redshift in the absorption spectra.
TL;DR: In this paper, the absorption spectrum of 3,3,disulfopropyl-5,5,dichlorothiacyanine sodium salt (TC) is characterized by an evident absorption dip at the position corresponding to the J-band of TC.
Abstract: Au, Ag, and Au/Ag colloidal nanoparticles coated with the J-aggregate of an anionic cyanine dye, 3,3‘-disulfopropyl-5,5‘-dichlorothiacyanine sodium salt (TC), have been prepared for the first time. The absorption spectrum of TC-coated Au colloidal nanoparticles is not a simple sum of the contributions of colloidal gold and TC but is characterized by an evident absorption dip at the position corresponding to the J-band of TC. These spectral features are reproduced by the simulation based on the Maxwell−Garnett-type treatment of Gao et al. The alternate adsorption technique allowed us to deposit dye-coated Au/Ag composite nanoparticles at the surface of a cationic polymer, poly(diallyldimethylammonium chroride).
TL;DR: A specific hypothesis on the mechanism of dioxygen formation during the S(3)-(S(4))-S(0) transition is presented, according to this hypothesis, water oxidation is facilitated by manganese reduction that is coupled to proton transfer from a substrate water to bridging oxides.
TL;DR: In this paper, photogenerated electrons trapped in shallow mid-gap states were proposed to originate the transient absorption and the decay kinetics of the trapped electrons were fitted to a multi-exponential formula with six lifetimes ranging from 1×10−7 to 3× 10−1 s.
TL;DR: In this paper, the authors reanalyzed the Chandra HETGS spectrum using better flux and wavelength calibrations, along with more robust methods to demonstrate the existence of the absorption lines and determine that they are blueshifted relative to the systemic velocity by -610? 130 km s-1.
Abstract: The high-resolution X-ray spectrum of NGC 3783 shows several dozen absorption lines and a few emission lines from the H-like and He-like ions of O, Ne, Mg, Si, and S, as well as from Fe XVII-Fe XXIII L-shell transitions. We have reanalyzed the Chandra HETGS spectrum using better flux and wavelength calibrations, along with more robust methods. Combining several lines from each element, we clearly demonstrate the existence of the absorption lines and determine that they are blueshifted relative to the systemic velocity by -610 ? 130 km s-1. We find the Ne absorption lines in the High-Energy Grating spectrum to be resolved with FWHM = 840 km s-1; no other lines are resolved. The emission lines are consistent with being at the systemic velocity. We have used regions in the spectrum where no lines are expected to determine the X-ray continuum, and we model the absorption and emission lines using photoionized-plasma calculations. The model consists of two absorption components, with different covering factors, which have an order-of-magnitude difference in their ionization parameters. The two components are spherically outflowing from the active galactic nucleus, and thus contribute to both the absorption and the emission via P Cygni profiles. The model also clearly requires O VII and O VIII absorption edges. The low-ionization component of our model can plausibly produce UV absorption lines with equivalent widths consistent with those observed from NGC 3783. However, we note that this result is highly sensitive to the unobservable UV to X-ray continuum, and the available UV and X-ray observations cannot firmly establish the relationship between the UV and X-ray absorbers. We find good agreement between the Chandra spectrum and simultaneous ASCA and RXTE observations. The 1 keV deficit previously found when modeling ASCA data probably arises from iron L-shell absorption lines not included in previous models. We also set an upper limit on the FWHM of the narrow Fe K? emission line of 3250 km s-1. This is consistent with this line originating outside the broad-line region, possibly from a torus.
TL;DR: In this paper, the absorption spectra of Ag5-8 have been determined in the framework of the linear response equation-of-motion coupled cluster method and related techniques employing 11-electron relativistic effective core potential.
Abstract: The absorption spectra of Ag5–8 have been determined in the framework of the linear response equation-of-motion coupled cluster method and related techniques employing 11-electron relativistic effective core potential. In these treatments electron correlation effects for 11 electrons per atom are included, providing an accurate description of excited states of silver clusters. The calculations of transition energies and oscillator strengths have been carried out in a large energy interval for the stable structures and for the isomeric forms higher in energy. This allowed us to investigate the influence of structural properties on the spectroscopic patterns and to determine the role of d-electrons. Inclusion of d-electrons in the correlation treatment is mandatory to obtain accurate values for transition energies, but the excitations of s-electrons are primarily responsible for the spectroscopic patterns. They are characterized by the interference phenomena known in molecular spectroscopy which lead to a s...
TL;DR: In this paper, the in situ X-ray absorption fine structure (XAFS) technique was used to study the chemical states and structural changes accompanying the electrochemical Li deintercalation of Li1−x(Mn, M)2O4 (M=Cr, Co, Ni).
TL;DR: The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (FWHM - 1400 km/s) absorption lines from highly ionized elements including hydrogen- and helium-like carbon, nitrogen, oxygen, and neon, and several iron L - shell ions (Fe XVII - XX).
Abstract: The luminous infrared-loud quasar IRAS 13349+2438 was observed with the XMM - Newton Observatory as part of the Performance Verification program. The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (FWHM - 1400 km/s) absorption lines from highly ionized elements including hydrogen- and helium-like carbon, nitrogen, oxygen, and neon, and several iron L - shell ions (Fe XVII - XX). Also shown in the spectrum is the first astrophysical detection of a broad absorption feature around lambda = 16 - 17 A identified as an unresolved transition array (UTA) of 2p - 3d inner-shell absorption by iron M-shell ions in a much cooler medium; a feature that might be misidentified as an O VII edge when observed with moderate resolution spectrometers. No absorption edges are clearly detected in the spectrum. We demonstrate that the RGS spectrum of IRAS 13349+2438 exhibits absorption lines from two distinct regions, one of which is tentatively associated with the medium that produces the optical/UV reddening.