Development of optical methods for simultaneous detection of I2, I−, IO 3 − , and I 3 − in liquid media in real Time

The absorption spectra of IO₃⁻ in liquid media are experimentally studied in the UV spectral range. The absorption cross sections are determined in the range 200–265 nm. The results are used to propose an optical method for the real-time simultaneous detection of molecular iodine and the I⁻, IO₃⁻ and I₃⁻¹ anions in liquid media. The measurement sensitivity for the above substances is sufficient for monitoring of the kinetics of physicochemical reactions that take place at various stages of processing of the spent nuclear fuel. This circumstance makes it possible to increase the efficiency and improve the ecological safety of the process.     

X-ray photoelectron spectra and atom valency distribution in oxide BaPb1−xBixO3 superconductor

X-ray photoelectron spectra of valent regions and inner atomic levels for BaPb_0.8Bi_0.2O₃, PbO, PbO₂, BaPbO₃, BaBiO₃, NaBiO₃, Bi₂O₃ have been measured. On the basis of the comparison of bond energy values 4f_7/2 Pb for PbO (137.9 eV), PbO₂ (136.9 eV), BaPbO₃ (137.8 and 136.6 eV) and bond energy values 4f_7/2 Bi for BaBiO₃ (158.4 and 157.5 eV), NaBiO₃ (157.6 eV), Bi₂O₃ (158.2 eV) with analogous values 4f_7/2 Pb (137.7 and 136.9 eV) and 4f_7/2 Bi (158.2 and 157.4 eV) for studied BaPb_0.8Bi_0.2O₃ it is strictly shown that two valent forms of lead atoms Pb^IV, Pb^II and two valent forms of bismuth atoms Bi^V, Bi^III are simultaneously present in the structure of the high temperature oxide superconductor BaPb_0.8Bi_0.2O₃. The parameters of X-ray photoelectron spectra of valent regions of all studied compounds do not contradict this conclusion about the valent states of lead and bismuth atoms in the BaPb_0.8Bi_0.2O₃ structure.     

Effects of shape and dopant on structural,optical absorption,Raman, and vibrational properties of silver and copper quantum clusters: A density functional theory study

We investigate the effects of shape and single-atom doping on the structural, optical absorption, Raman, and vibra- tional properties of Ag13, Ag12CUl, CUl3, and Cul2Agl clusters by using the （time-dependent） density functional the- ory. The results show that the most stable structures are cuboctahedron （COh） for Ag13 and icosahedron （Ih） for CUl3, Agl2CUlcore, and Cul2Aglsur. In the visible-near infrared optical absorption, the transitions consist of the interband and the intraband transitions. Moreover, red shifts are observed as follows： 1） clusters change from Agl2CUlcore to Ag13 to Ag12Culsur with the same motifs, 2） the shapes of pure Agl3 and Agl2CUlcore clusters change from COh to Ih to decahe- dron （Dh）, 3） the shape of Agl2CUlsur clusters changes from Ih to COh to Dh, and 4） the shapes of pure CU13 and Cu12Agl clusters change from Ih to Dh to COb. All of the Raman and vibrational spectra exhibit many significant vibrational modes related to the shapes and the compositions of the clusters. The ranges of vibrational spectra of Ag13, Agl2CUl or CU13, and Cu12Agl clusters become narrower and the vibrational intensities increase as the shape of the clusters changes from Ih to Dh to COh.     

X-ray photoelectron spectra and composition of YBa2Cu3O7 − δ films prepared by laser ablation

The Y3d, Ba3d _5/2, Cu2p _3/2, and O1s X-ray photoelectron spectra of thick (600 nm) superconducting YBa₂Cu₃O_{7 ? δ} films deposited on textured Ni-W substrates with Y₂O₃ + ZrO₂ and CeO₂ buffer layers have been studied. It has been established that, after the mechanical removal of surface layers with a diamond scraper (and as the analyzed region of the film approaches the interface), a decrease in the oxygen content leads to a decrease of the orthophase fraction and an increase of the tetraphase and Cu⁺ ion fractions. This is caused by the presence of elastic stresses in the superconducting film due to the lattice misfit between the phases making up a composite sample. These stresses prevent oxygen diffusion involved in oxidizing annealing. The spectra of the superconducting film have not revealed signals generated by elements of the substrate and buffer layers.     

K − absorption in nuclei by two and three nucleons

It will be shown that the peaks in the (Λp) and (Λd) invariant mass distributions, observed in recent FINUDA experiments and claimed to be signals of deeply bound kaonic states, are naturally explained in terms of K ^? absorption by two or three nucleons leaving the rest of the original nuclei as spectator. For reactions on heavy nuclei, the subsequent interactions of the particles produced in the primary absorption process with the residual nucleus play an important role. Our analyses leads to the conclusion that at present there is no experimental evidence of deeply bound K ^? state in nuclei. Although the FINUDA experiments have been done for reasons which are not supported a posteriori, some new physics can be extracted from the data.     

Dynamics of iron in Fe-porphyrin aggregates studied by X-ray absorption and Mössbauer spectroscopy

The iron-porphyrin aggregates were studied by optical absorption and fluorescence method, infrared spectroscopy, X-ray absorption and Mössbauer spectroscopy. The aggregation of porphyrin molecules strengthens the Fe-ligands bonds and accelerates the spin-spin relaxations. A significant speeding-up of relaxation was observed with lowering the temperature down to 25 K. The comparison of the EXAFS (Extended X-ray Absorption Fine Structure) and Mössbauer spectroscopy results enabled some separation of the individual Fe vibration from its collective movement with ligands.     

Thermoluminescence and ESR phenomena in X-ray irradiated mixed alkaline-alkaline earth metal sulfates—I

Abstract

Thermoluminescence (TL) and ESR phenomena induced by X-ray irradiation of the mixed samples of K₂SO₄ and alkaline earth metal sulfate (MgSO₄ or BaSO₄) were investigated in terms of the reactivities and the crystallogrpahic properties. A high intensive TL resulted from the diffusion of a small amount of Mg²⁺ into K₂SO₄ crystals. The amount formed of K₂Mg₂(SO₄)₃, langbeinite, compound had a maximum at the stoichiometric composition. From the ESR measurements, SO^? ₃ radicals were found to be easily formed in the langebeinite by excitation. Both the TL and the ESR phenomena were hardly observed in the K₂SO₄–BaSO₄ system due to little diffusion of Ba²⁺ with much larger radius than Mg²⁺. The results were mainly discussed on the basis of the radii of the component cations in these systems. In addition, the fundamental data as to the application to the ESR dosimetry were obtained.     

X-ray photoelectron and X-ray absorption spectroscopic study on β-FeSi2 thin films fabricated by ion beam sputter deposition

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of β-FeSi₂ films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO₂ layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi_2−X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi₂ with α and ? phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous β-FeSi₂. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous β-FeSi₂. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.     

Study on the interaction of anticancer drug mitoxantrone with DNA by fluorescence and Raman spectroscopies

Mitoxantrone, a clinically useful antitumour antibiotic for leukaemia and breast cancer, has received more attentions. In this paper, the interaction between mitoxantrone and calf thymus DNA is investigated by Raman and fluorescence spectroscopies, and the binding site of mitoxantrone to calf thymus DNA is explored. The results showed that mitoxantrone interacts with calf thymus DNA bases by the intercalation of anthracycline into the base pair plane of adenine (A) and thymine (T), and it results in the disruption of the hydrogen bonds between calf thymus DNA bases, and thus the calf thymus DNA double-strand can be disrupted into the B-form DNA double-strand segments.     

Ab initio and anion photoelectron studies of Rhn (n = 1 − 9) clusters

We present an analysis of Na-He collisional profiles at high density and very low temperature in a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. Clearly understanding the variation of shape of the two fine-structure components of the 3s?3p line with increasing helium density allows us to understand experimental spectra of a Na atom attached to He nanodroplets. We compare our collisional approach to path integral Monte Carlo calculations using the same ab initio Na-He molecular potentials.     

XRD,Raman and magnetic studies of Bi1−xLaxFeO3 solid solution obtained by mechanochemical synthesis

ABSTRACT

Bi_{1 ? x}La_xFeO₃ single-phase solid solution with 0 ≤ x ≤ 0.3 was obtained by mechanochemical synthesis and characterized by X-ray diffraction, FT NIR Raman spectroscopy and magnetic studies. The nanocrystalline powders of rhombohedrally distorted perovskite structure R3c were studied ‘as synthesized’ by mechanosynthesis and after annealing at 500 °C for 1 h. The annealing, which resulted in recrystallization of the amorphous shell of the nanograins, was found to modify the external lattice modes of Bi_1?xLa_xFeO₃ and resulted in changes in the temperature variation of the magnetization.     

Synthesis and optical properties of La1−XCeXMnO3 studied by infrared reflectivity measurements

The bulk polycrystalline La_1−xCe_xMnO₃ (0.0 ≤ x ≤ 0.8) manganites were synthesized through citrate sol-gel auto-combustion method for a wide range of composition 0.0 ≤ x ≤ 0.8. The x-ray diffraction (XRD) analysis suggests the single phase rhombohedral (R-3c) symmetry for parent LaMnO₃ compound, however a secondary cubic (Fm-3 m) phase of cerium oxide (CeO₂) is appeared when Ce is incorporated into the LaMnO₃. A detailed XRD study of these materials were discussed, and specifically the infrared reflectivity measurements on La_1−xCe_xMnO₃ materials are discussed in this study for the first time. The phonon softening and hardening was observed for different modes but softening was found to be more pronounced which implied strong electron–phonon coupling. The most affected phonon mode was appeared for the doping range 0.2 ≤ x ≤ 0.4, in which the largest softening was observed. The Lyddane–Sachs–Teller relation is verified by experimental FTIR data.     

Valence band offset of ZnO/BaTiO3 heterojunction measured by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset of the ZnO/BaTiO₃ heterojunction grown by metal-organic chemical vapor deposition. The valence band offset (VBO) is determined to be 0.48±0.09 eV, and the conduction band offset (CBO) is deduced to be about 0.75 eV using the band gap of 3.1 eV for bulk BaTiO₃. It indicates that a type-II band alignment forms at the interface, in which the valence and conduction bands of ZnO are concomitantly higher than those of BaTiO₃. The accurate determination of VBO and CBO is important for use of semiconductor/ferroelectric heterojunction multifunctional devices.     

Models of optical absorption in amorphous semiconductors at the absorption edge — A review and re-evaluation

Davis-Mott and Tauc models of optical absorption at the absorption edge in the high absorption coefficient region (10⁴cm^–1) are carefully reviewed with regard to their theoretical foundations, assumptions, mathematical derivations, and results. The full implications of these models are exploited, and it is found that the Davis-Mott model for negligible matrix elements between localised states could account for the cubic power law behaviour of with photon energy of some amorphous semiconductors such as a-Si. A fractional power law to find the optical band gapE _opt, of the form [ (–E _opt)^r; 2r3] based on Davis-Mott model is proposed in which the indexr can be a function of disorder. The Tauc model has further been extended to the case of negligible matrix elements between localised states, in which the same square power law for vs. with the same meaning of the optical gap as in the original Tauc model has resulted. A consideration of the case of unequal matrix elements for those transitions between localised states and those between extended states is also included. The meaning ofE _opt has been re-assessed and it is emphasized that it is an extrapolation of delocalised states to the zero of the density of states rather than a threshold energy for the onset of some kind of optical transitions.This paper is cordially dedicated to Professor C. A. Hogarth who taught us the Physics of amorphous materials.     

FTIR and optical properties for irradiated PVA–GdCl3 and its possible use in dosimetry

There are various chemical and physical changes caused when polymers are exposed to a source of radiation. In the present work, four films of polyvinyl alcohol (PVA) doped with 2, 4, 6 and 8 wt% of gadolinium chloride (GdCl₃) have been irradiated by low-dose fast neutrons using Am-241/Be-9. The structural properties of the synthesized films have been investigated pre- and post-irradiation on the basis of Fourier transform infrared technique. The optical properties of the PVA–GdCl₃ films have been investigated for doses up to 1.2 KGy. The energy gap of the synthesized films showed a neutron dose dependence and was decreased by 0.81 eV after exposing to 1.2 kGy. At a wavelength of 1000 nm, the refractive index of the PVA doped with 8 wt% GdCl₃ has been increased by nearly 16%. The results suggested the possible use of PVA--GdCl₃ as a dosimeter for the neutron beams.     

Structural and compositional mapping of a phase-separated Langmuir–Blodgett monolayer by X-ray photoelectron emission microscopy

The structure and composition of phase-separated Langmuir–Blodgett monolayer films comprised of mixtures of arachidic acid (C₁₉H₃₉COOH) and perfluorotetradecanoic acid (C₁₃F₂₇COOH) were characterized using a combination of X-ray photoelectron emission microscopy (X-PEEM), secondary electron emission microscopy (SEEM) and atomic force microscopy (AFM). X-PEEM provides high lateral spatial resolution and is directly sensitive to the elemental and chemical (functional group) composition of these ultrathin films through the chemical sensitivity of NEXAFS spectroscopy; AFM provides high-resolution imaging, both in terms of lateral and vertical (height) film topography. SEEM provides additional structural and electronic information through work function and electron scattering effects. The combination is used for chemical mapping of the phase-separated domains in the monolayer film. Our results directly confirm previous AFM measurements that suggested that the discontinuous domains are enriched in arachidic acid, whereas the surrounding continuous domain is a mixture of both arachidic acid and perfluorotetradecanoic acid.     

Optimization of Paris–Edinburgh press cell assemblies for in situ monochromatic X-ray diffraction and X-ray absorption

We describe some important improvements allowed by the development of new cell assemblies coupled to opposed conical sintered diamond anvils in the Paris–Edinburgh press. We provide X-ray absorption and diffraction experiments carried out at pressures up to 16.5 GPa. The maximum temperature reached was 1800 K for P<10 GPa and 1300 K for higher pressures. The sintered diamond anvils are X-ray transparent and give access to a much larger X-ray window than the tungsten carbide anvils, even at the highest pressure. Therefore, X-ray measurements are performed using in situ cross-calibration simultaneously. We also describe a new heating setup used to reach high temperatures, despite the low conductivity of the sintered diamond core by deviating the electrical current using copper strips. These improvements are illustrated by recent data collected using angle dispersive in situ X-ray diffraction on liquid Fe-18%wt S and using EXAFS at the barium K-edge on Ba₈Si₄₆ silicon clathrates and at the iodine K-edge on iodine-intercalated nanotubes.     

Nonlinear optical absorption and refraction in Ru, Pd, and Au nanoparticle suspensions

We present the results of studies of the nonlinear optical properties of Pd, Ru, and Au nanoparticles. We studied the nonlinear refraction and nonlinear absorption of suspensions of these nanoparticles at 1064-nm wavelength. A relatively strong nonlinear absorption of the Pd nanoparticles was observed in the case of 1064-nm, 50-ps pulses (β=2×10⁻⁹ m W⁻¹). The Ru and Pd nanoparticles showed weak negative nonlinear refraction (γ∼−(6–8)×10⁻¹⁶ m² W⁻¹) in this spectral range. In the case of the Au nanoparticles, a saturated absorption at 532 nm dominated over other nonlinear optical processes.     

X-ray absorption spectroscopy of the 90K superconductor YBa2Cu3O7−δ

X-ray absorption spectroscopy has been used to probe the Cu environment of the new highT _c YBa₂Cu₃O_7– superconductor. Evidences of other valencies than two are found for copper. Besides Cu¹⁺ which is localized on Cu₁ sites when the unit cell is oxygendeficient, one invokes a ground state which merges bivalent 3d ⁹ to 3d ⁹ L configurations as proposed in a recent paper (L stands for a ligand hole in the CuO bond) very similar to that observed in many light rare earth oxides.