Showing papers on "Chemical state published in 2007"
TL;DR: In this paper, Tungsten oxide (WO3) nanowires were prepared on a tungsten substrate by thermal evaporation of WO3 powder at elevated temperature in a tube furnace.
Abstract: Tungsten oxide (WO3) nanowires were prepared on a tungsten (W) substrate by thermal evaporation of WO3 powder at elevated temperature in a tube furnace. The morphology, structure, composition, and chemical state of the prepared nanowires were characterized by SEM, EDX, TEM, XRD, Raman spectroscopic, and XPS measurements. The nanowires grown using WO3 powder were found to have uniform morphology with a high density and a crystalline structure consistent with monoclinic WO3. The field-emission measurements showed that the prepared nanowires have a turn-on field of 4.8 V/μm. The role of WO3 powder in the growth of high-density nanowires has been discussed by comparing the above results with those of nanowires grown without using WO3 powder and also on a different substrate. Also, the effects of growth temperature on the chemical binding states and product morphology of the nanowires were investigated.
199 citations
TL;DR: In this article, the technical aspects of high-pressure X-ray photoelectron spectroscopy (XPS) were discussed and applications of this technique to catalytic reactions on metal surfaces were discussed.
Abstract: X-ray photoelectron spectroscopy (XPS) is a quantitative, chemically specific technique with a probing depth of a few angstroms to a few nanometers. It is therefore ideally suited to investigate the chemical nature of the surfaces of catalysts. Because of the scattering of electrons by gas molecules, XPS is generally performed under vacuum conditions. However, for thermodynamic and/or kinetic reasons, the catalyst's chemical state observed under vacuum reaction conditions is not necessarily the same as that of a catalyst under realistic operating pressures. Therefore, investigations of catalysts should ideally be performed under reaction conditions, that is, in the presence of a gas or gas mixtures. Using differentially pumped chambers separated by small apertures, XPS can operate at pressures of up to 1 Torr, and with a recently developed differentially pumped lens system, the pressure limit has been raised to about 10 Torr. Here, we describe the technical aspects of high-pressure XPS and discuss recent applications of this technique to oxidation and heterogeneous catalytic reactions on metal surfaces.
178 citations
TL;DR: In this article, a uniform CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via the sol-gel method.
Abstract: Uniform CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via the sol–gel method. The samples were characterized using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The surface state analysis by means of X-ray photoelectron spectroscopy (XPS) shows that the Ti element mainly exists as a chemical state of Ti4+, while the Ce element exists as a mixture of Ce3+ and Ce4+ oxidation states. The photocatalytic degradation of methyl orange (MeO) in CeO2/TiO2 suspension was investigated. The results indicate that the CeO2/TiO2 nanocomposites show higher photocatalytic activity than pure TiO2. Photodegradation of MeO can be improved by increasing the Ce/Ti molar ratio in the initial 15 min.
85 citations
TL;DR: In this paper, two Raman peaks were observed at 274 and 580 cm−1 and the nitrogen activation at 500°C [the activation temperature (AT)] has been obtained according to the variation of the integral intensity of these two peaks.
Abstract: N-doped ZnO films were prepared by annealing zinc oxynitride films deposited by rf reactive sputtering. Two Raman peaks were observed at 274 and 580 cm−1. According to the variation of the integral intensity of these two peaks, the nitrogen activation at 500 °C [the activation temperature (AT)] has been obtained. Below the AT, the integral intensities of them show a different variation trend. X-ray photoelectron spectroscopy (XPS) indicates the N chemical state variation for them and finds the activated Zn-N bond. Further analyses by photoluminescence (PL) spectra and spectroscopic ellipsometry (SE) have been carried out. The activated sample exhibits a symmetric emission peak at 3.22 eV assigned to be the AX0 emission at room temperature. SE investigation takes account of samples within the different temperature span divided by the AT. Different factors, such as nitrogen dopant (N)O and the nanocrystal growth, which affect the redshift of the absorption edges, have been discussed.
72 citations
TL;DR: In this paper, two different metal loading methods were used to prepare Fe-MCM-41 catalysts for polyethylene, polymethylmetacrylate and polystyrene.
64 citations
TL;DR: In this paper, Nitrogen incorporation in HfO2∕SiO2 films utilized as high-k gate dielectric layers in advanced metal-oxide-semiconductor field effect transistors has been investigated.
Abstract: Nitrogen incorporation in HfO2∕SiO2 films utilized as high-k gate dielectric layers in advanced metal-oxide-semiconductor field effect transistors has been investigated Thin HfO2 blanket films deposited by atomic layer deposition on either SiO2 or NH3 treated Si (100) substrates have been subjected to NH3 and N2 anneal processing Several high resolution techniques including electron microscopy with electron energy loss spectra, grazing incidence x-ray diffraction, and synchrotron x-ray photoelectron spectroscopy have been utilized to elucidate chemical composition and crystalline structure differences between samples annealed in NH3 and N2 ambients as a function of temperature Depth profiling of core level binding energy spectra has been obtained by using variable kinetic energy x-ray photoelectron spectroscopy with tunable photon energy An “interface effect” characterized by a shift of the Si4+ feature to lower binding energy at the HfO2∕SiO2 interface has been detected in the Si 1s spectra; however, no corresponding chemical state change has been observed in the Hf 4f spectra acquired over a broad range of electron take-off angles and surface sensitivities The Si 2p spectra indicate Si–N bond formation beneath the HfO2 layer in the samples exposed to NH3 anneal The NH3 anneal ambient is shown to produce a metastable Hf–N bond component corresponding to temperature driven dissociation kinetics These findings are consistent with elemental profiles across the HfO2∕Si(100) interface determined by electron energy loss spectroscopy measurements X-ray diffraction measurements on similarly treated films identify the structural changes resulting from N incorporation into the HfO2 films
63 citations
TL;DR: In this paper, the authors studied the correlation between the chemical state and the oxygen-sensing properties of an iron oxide thin film using a setup that allows simultaneous sensor resistance measurements and X-ray photoelectron spectroscopy (XPS) data acquisition.
62 citations
TL;DR: In this article, an iron addition was attempted in order to improve the pseudo-capacitive property of Mn oxides, and the results indicated that the incorporated iron presented as divalent and trivalent forms in the binary oxides.
Abstract: Iron addition was attempted in this study to improve the pseudo-capacitive property of Mn oxides. The oxides were prepared on graphite substrates by anodic deposition. The deposition solutions were 0.25 M manganese acetate MnCH3COO2 aqueous solutions with various amount of FeCl3 up to 0.15 M. Crystal structure and surface morphology of the deposited oxides were examined by X-ray diffraction and scanning electron microscopy, while their chemical state was analyzed by X-ray photoelectron spectroscopy and X-ray absorption near edge structure. Moreover, specific capacitances of the oxide electrodes were determined by cyclic voltammetry in 2 M KCl electrolyte. Experimental results indicated that the incorporated iron presented as divalent and trivalent forms in the binary oxides. Although iron addition did not change the nanocrystalline structure of the deposited Mn oxide, it caused the chemical state and surface morphology variations of the oxide electrodes. Consequently, their pseudo-capacitive performances were modified. The optimum specific capacitance of 212 F g1 was found for the oxide deposited in the solution containing 0.05 M FeCl3. The value was 21% higher than that of the plain Mn oxide. Capacitance-retained ratio of the oxide after 1000 charge-discharge cycles was also improved from 70 to 85% because of iron addition.
48 citations
TL;DR: It has been shown that the composition of catalytically active steady states, exhibiting different activity and selectivity, evolves under the reaction conditions, independent of the crystallographic orientation and the initial pre-catalyst chemical state, metallic Ru or RuO(2).
Abstract: One of the prerequisites for the detailed understanding of heterogeneous catalysis is the identification of the dynamic response of the catalyst surface under variable reaction conditions. The present study of methanol oxidation on different model Ru pre-catalysts, performed approaching the realistic catalytic reaction conditions, provides direct evidence of the significant effect of reactants' chemical potentials and temperature on the catalyst surface composition and the corresponding catalytic activity and selectivity. The experiments were carried out for three regimes of oxygen potentials in the 10(-1) mbar pressure range, combining in situ analysis of the catalyst surface by synchrotron-based photoelectron core level spectroscopy with simultaneous monitoring of the products released in the gas phase by mass spectroscopy. Metallic Ru with adsorbed oxygen and transient 'surface oxide', RuO(x), with varying x have been identified as the catalytically active states under specific reaction conditions, favouring partial or full oxidation pathways. It has been shown that the composition of catalytically active steady states, exhibiting different activity and selectivity, evolves under the reaction conditions, independent of the crystallographic orientation and the initial pre-catalyst chemical state, metallic Ru or RuO(2).
46 citations
TL;DR: The stability of the CuO(x)/TiO(2) catalysts with different copper loading was also studied with respect to carbonaceous deposits and copper leaching.
45 citations
TL;DR: In this paper, an ion implantation of ions into the near surface layer is proposed to improve the osseointegration of metallic biomaterials like titanium, which is well known that surface topography and surface physico-chemistry as well as visco-elastic properties influence the cell response after implantation into the human body.
TL;DR: In this article, the formation of gold nanoparticles in radio frequency (RF) reactive magnetron co-sputtered Au-SiO 2 thin films post annealed at different temperatures in Ar + H 2 atmosphere has been investigated.
TL;DR: In this paper, the thermodynamic feasibility of formation of the metal via the reduction of the oxide by carbon (char) was examined using Ellingham diagrams, and the predictions agreed fairly well with the XRD results.
Abstract: Samples of carboxy methyl cellulose, subjected to ion exchange with different metal ions (Cu, Ni, Co, Fe, and Ca), were pyrolyzed in the temperature range of 300−1000 °C to obtain chars that were doped with metal species. X-ray diffraction (XRD) profiles of these chars showed that the metal species in the char existed as an oxide or elemental metal or carbide, depending on the heat-treatment temperature. The thermodynamic feasibility of formation of the metal via the reduction of the oxide by carbon (char) was examined using Ellingham diagrams, and the predictions agreed fairly well with the XRD results. The XRD peaks of metals were observed near the predicted temperatures. However, metal oxides showed their peaks only at temperatures higher than the temperatures of their formation, possibly because of their high Tammann temperatures and their nanodispersion in the char matrix. The Ellingham diagrams, in combination with XRD data, provide valuable insight into the chemical state of the catalyst species in...
TL;DR: In this article, the adsorption of submonolayer V on an idealized model hematite (0, 0, 0, 1) surface and subsequent oxidation under atomic O adsorptions are studied by density functional theory.
TL;DR: To demonstrate a chemical state analysis using the high-resolution PIXE system, Si Kalpha(1,2) and Kbeta x-ray spectra for SiC, Si(3)N(4), and SiO(2) were measured and compared and the tendency of these shifts were well explained by the effective charges of the silicon atoms calculated by a molecular orbital method.
Abstract: We have developed a high-efficiency high-resolution particle-induced x-ray emission (PIXE) system employing a von Hamos-type crystal spectrometer for a chemical state identification of trace elements in environmental samples. The energy resolution of the system was determined to be about 0.05% through the observation of Si Kalpha(1,2) x rays (1.74 keV) from elemental silicon. The throughput efficiency of the system was also evaluated quasitheoretically to be 1.6x10(-7) counts/incident proton for Si Kalpha(1,2) emission. To demonstrate a chemical state analysis using the high-resolution PIXE system, Si Kalpha(1,2) and Kbeta x-ray spectra for SiC, Si(3)N(4), and SiO(2) were measured and compared. The observed chemical shifts of the Si Kalpha(1,2) peaks for SiC, Si(3)N(4), and SiO(2) relative to elemental silicon were 0.20, 0.40, and 0.55 eV, respectively. The tendency of these shifts were well explained by the effective charges of the silicon atoms calculated by a molecular orbital method.
TL;DR: It turns out that the (4 x 4)O structure only forms under extremely clean conditions, indicating that the(4 x4)O phase and similar oxygen-induced reconstructions of the Ag(111) surface are chemically unstable.
Abstract: To identify surface phases that could play a role for the epoxidation of ethylene on Ag catalysts we have studied the interaction of Ag(111) with O2 at elevated pressures. Experiments were performed using high-pressure scanning tunneling microscopy (STM) at temperatures between 450 and 480 K and O2 pressures in the mbar range. Below p(O2) ∼1 mbar the surface largely showed the structure of bare Ag(111). At p(O2) above ∼1 mbar the (4 × 4)O structure and the closely related (4 × 5√3)rect structure were observed. The findings confirm theoretical predictions that the (4 × 4)O structure is thermodynamically stable at the oxygen partial pressure of the industrial ethylene oxide synthesis. However, in other experiments only a rough, disordered structure was observed. The difference is caused by the chemical state of the STM cell that depends on the pretreatment and on previous experiments. The surface was further analyzed by X-ray photoelectron spectroscopy (XPS). Although these measurements were performed after sample transfer to ultra-high vacuum (UHV), so that the surface composition was modified, the two surface states could still be identified by the presence of carbonate or a carbonaceous species, and by the absence or presence of a high-binding energy oxygen species, respectively. It turns out that the (4 × 4)O structure only forms under extremely clean conditions, indicating that the (4 × 4)O phase and similar oxygen-induced reconstructions of the Ag(111) surface are chemically unstable. Chemical reactions at the inner surfaces of the STM cell also complicate the detection of the catalytic formation of ethylene oxide.
TL;DR: In this article, the binding energy of the Ti 2p lines is consistent with only one chemical state, Ti 4+, and the presence of Pb 0 state on the surface of all samples was due to the reduction of lead ions caused by the preferential removal of the oxygen ions after sputtering.
TL;DR: In this article, the thermal stability of nitrogen-doped SrTiO3 (001) films in terms of electronic and optical properties has been studied by using x-ray photoemission spectroscopy.
Abstract: The thermal stability of nitrogen-doped SrTiO3 (001) films in terms of electronic and optical properties has been studied by using x-ray photoemission spectroscopy, x-ray absorption spectroscopy, and spectroscopic ellipsometry techniques. The chemical states of nitrogen in nitrogen-doped SrTiO3 films include both substitutional and interstitial states. The N 2p states localized above the O 2p-derived valence band maximum are attributed to the change of optical properties. Postannealing will induce the valence band edge shift due to the thermal instability of interstitial N states, which may degrade the photocatalysis of nitrogen-doped SrTiO3 films during applications.
TL;DR: In this paper, depth-resolved EELS (DREELS) and chemical state mapping were applied to the cross-sectional TEM (XTEM) sample of N + implanted TiO 2 catalyst.
Abstract: We propose novel methods of depth-resolved EELS (DREELS) and chemical state mapping, and the techniques were applied to the cross-sectional TEM (XTEM) sample of N + implanted TiO 2 catalyst. DREELS is realized by applying the Pixon deconvolution to a conventional energy-filtering TEM (EFTEM)-based spatially resolved EELS (EFTEM-SREELS), demonstrated by Kimoto et al. [J. Electron Microsc. 46 (1997) 369-374.]. And a self-modeling curve resolution (SMCR) technique in multivariate analysis enabled chemical state mapping from EFTEM-based spectrum imaging (EFTEM-SI) data sets. The methods successfully extracted the depth dependence of the N-K ELNES and separately displayed the spatial distributions of the constituent chemical states, whose spectral features were overlapped.
TL;DR: In this paper, the authors analyzed the chemical state of sulfur on silver and copper plates exposed to flowing air containing low concentrations (18 and 148 ppb) of SO2 using X-ray photoelectron spectroscopy (XPS).
Abstract: Sulfur dioxide (SO2) is a typical gas affecting the atmospheric corrosion of metals, particularly outdoors. Although many studies have investigated the effect of SO2 on the atmospheric corrosion of silver and copper, little is known about the early stage of their corrosion behavior. In this study we analyzed the chemical state of sulfur on silver and copper plates exposed to flowing air containing low concentrations (18 and 148 ppb) of SO2 using X-ray photoelectron spectroscopy (XPS). The shapes of the spectra were the same for both concentrations, indicating that the chemical state of the analyzed elements did not depend on the SO2 concentration. There was a difference in the chemical state of the sulfur between the silver and copper. Three peaks were observed in the S 2p XPS spectra for the silver originating from bisulfite, S2O52-, S2O32-, and S2-. The bisulfite resulted from SO2 dissolution into the surface electrolyte, and the others resulted from the reduction of sulfurous acid. In contrast, only bisulfite was observed in the S 2p XPS spectra for the copper. It also originated from the dissolution of SO2 into the surface electrolyte. The difference in the chemical state of the sulfur between the silver and copper is attributed to the presence of native oxides on the surface, which may have impeded the reduction of bisulfite.
TL;DR: In this article, the chemical state of semiconducting and metallic SmS thin films by X-ray photoelectron spectroscopy were fabricated using dual-target magnetron sputtering by controlling the power applied to both metal and chalcogenide targets.
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) and XAFS were used to estimate Pu penetration depth and provide information about its chemical state.
TL;DR: In this article, the X-ray absorption near-edge structure (XANES) spectra of Cr, Mn, Cu and Zn were measured and compared with that of reference materials to obtain speciation information.
Abstract: The atmospheric particulate matter samples were collected in Shanghai, China. The X-ray absorption near-edge structure (XANES) spectra of Cr, Mn, Cu and Zn were measured. The XANES spectroscopy was used as a fingerprint to compare with that of reference materials to obtain speciation information. The oxidation state of these elements and main chemical components in the samples were described using the method. The results show that in our samples the oxidation state of Cr is trivalent, Mn mainly exists in the divalent state, Cu also exists in the divalent state, and Zn mainly exists in the zinc sulfate. For the XANES spectra of samples with different particle size and from different sampling site, we did not find their obvious differences. When we compared the XANES spectra of our samples with those of standard reference material SRM 1648, we found that they are similar in regards to the determined elements. The elemental concentrations in the samples were determined by proton induced X-ray emission (PIXE). The difference of elemental concentrations was observed in the different samples.
TL;DR: In this article, three W x C y thin films with different compositions were studied in order to correlate their properties with the thin-film composition and chemical bonding of C and W atoms.
TL;DR: In this article, the bimetallic, 20 wt % Pt 4 Mo/C electrocatalyst prepared by the colloidal aluminum-organic reductive-stabilization pathway by the Bonnemann's group was studied by means of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements aiming to a deeper insight on the structure, chemical state, catalytic and electrocatalytic functioning under CO/H 2 mixtures.
Abstract: The bimetallic, 20 wt % Pt 4 Mo/C electrocatalyst prepared by the colloidal aluminum-organic reductive-stabilization pathway by the Bonnemann's group (unpublished) was studied by means of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements aiming to a deeper insight on the structure, chemical state, catalytic and electrocatalytic functioning under CO/H 2 mixtures. Combined XPS and Ar + sputtering experiments revealed that Mo and Pt form bulk alloy nanoparticles, the surface of which is enriched with Pt atoms, while Mo 6+ (233.2 eV), Mo 5+ or Mo 4+ (231.5 eV) species exist on the nanoparticles' surface. PtMo nanoparticles are shown to be able to electrochemically oxidize CO at very low potential that coincides with the H 2 oxidation potential. This unique property depends on the oxidation state of the Mo surface species and specifically on the reactive OH species of MOO(OH) X and its attribute to spontaneously dissociate H 2 O. Due to this property PtMo nanoparticles can catalyze the water-gas shift reaction at temperatures as low as 60°C. However, the operation of the electrocatalyst at potentials higher than 0.15-0.2 V, with respect to the H 2 electrode voltage, results in the formation of MoO 3 and the deactivation of the low potential CO oxidation sites.
TL;DR: In this paper, a ball milling of an AlxTi(1-x) nanocomposite as Ti-containing starting material with NaH remains comparably stable upon cycling under hydrogen.
Abstract: The kinetics and hydrogen storage capacity of Ti-doped sodium alanate prepared by ball milling of an AlxTi(1-x) nanocomposite as Ti-containing starting material with NaH remain comparably stable upon cycling under hydrogen. The reaction rate of this material is comparable to that of TiCl3-doped samples. Extended X-ray absorption fine structure (EXAFS) analysis revealed that forming an AlxTi(1-x) nanocomposite by the reduction of TiCl4 by Al and subsequent annealing stabilizes the short-range order around Ti. The presence of stable Al−Ti phases at the beginning of the reaction prevents the subsequent formation of a Ti−Al cluster upon cycling under hydrogen, which is found in the case of doping with TiCl3. When the atomic-scale behavior of this new material is compared with that of the TiCl3- or Ti colloid-doped sodium alanates, it is found that the chemical state of Ti as well as its local structure seem to be relevant for the stability of the storage capacity and desorption/absorption reaction rate upon c...
TL;DR: In this article, the surface compositions of glass annealed at different temperatures and bombarded with Ar+ ions for various lengths of time have been determined using x-ray photoelectron spectroscopy.
Abstract: The elemental and ionic surface compositions of (TeO2)0.8 (WO3)0.2 and (TeO2)0.7(WO3)0.2(La2O3)0.1 glasses annealed at different temperatures and bombarded with Ar+ ions for various lengths of time have been determined using x-ray photoelectron spectroscopy. The results indicate that the surface layer of the glasses contains tellurium ions in two chemical states, which differ markedly in concentration. The oxidation state of one type of tellurium ion is close to that in TeO, \(E_{b_1 } \) (Te 3d5/2)= 574.0 eV, and the oxidation state of the other is close to that in TeO2 [\(E_{b_2 } \) (Te 3d5/2) = 576.6 eV. In all of the samples, tungsten is in an oxidation state close to 6+ (WO3), and the oxidation state of lanthanum is 3+ (La2O3). Ar+-ion milling for 4 min using an argon gun markedly reduces the surface hydrocarbon contamination but has, for the most part, an insignificant effect on the characteristics of the XPS spectra. Increasing the ion milling time leads to the formation of new states of both tellurium and tungsten ions. The oxygen ions in the glass samples studied are chemically equivalent and differ markedly in oxidation state from those in the constituent metal oxides. The metal—oxygen bond length evaluated from the O 1s binding energy in the glasses is RM-O = 0.192 nm.
TL;DR: In this paper, an X-EFM signal dependent on x-ray photon energy was used to obtain highly spatially resolved spectroscopic and image information of semiconductor surface region.
Abstract: Electrostatic force microscopy (EFM) was used to obtain highly spatially resolved spectroscopic and image information of semiconductor surface region. EFM with x-ray source (X-EFM) can probe x-ray induced photoionization of near surface electron trapping. The X-EFM signal dependent on x-ray photon energy results in nanometer scale x-ray absorption spectra. Furthermore, probing tip scanning at fixed x-ray photon energy provides chemical states imaging of the trapping. The authors demonstrate characterization of substoichiometric chemical oxidation of a Si surface with less than 1nm spatial resolution.
TL;DR: In this paper, chemical effects on the Li/Kj (i=α2, β, β1, β2; j=α, α 1, β 1), Li/Lα (i =l, β β, γ) and Li/kj ( i=l,α, β and γ; j =α1, α2) x-ray intensity ratios for Hf compounds were investigated.
Abstract: Chemical effects on the Ki/Kj (i=α2, β, β1, β2; j=α, α1, β1), Li/Lα (i=l, β, γ) and Li/Kj (i=l,α, β, γ; j=α1, α2) x-ray intensity ratios for (Hf) compounds were investigated. The samples were excited by 123.6 keV γ-rays from a 57Co annular radioactive source. K and L x-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. We observed a chemical effect on the Li/La and Li/Kj x-ray intensity ratios for Hf compounds. However, for the Ki/Kj intensity ratios, dependence on the chemical state of Hf compounds is almost negligible. The experimental values have been compared with the theoretically calculated values of pure Hf.
TL;DR: In this paper, the performance of multilayer interferential mirrors (MIMs) as Bragg dispersive devices for the analysis in wavelength dispersive spectrometry of samples containing N or Sc atoms is reported.
Abstract: The use of Cr∕Sc multilayer interferential mirrors (MIMs) in optical systems such as x-ray microscopes or telescopes have been reported for the water window (between C K- and O K-absorption edges). However, their possibilities in spectroscopic application have never been described in the literature. The purpose of the paper is to report for the first time on the performances of Cr∕Sc MIMs as Bragg dispersive devices for the analysis in wavelength dispersive spectrometry of samples containing N or Sc atoms. The possibility to distinguish the chemical state of the emitting N or Sc atoms is evidenced by using Johan-type and double-crystal spectrometers.