Raman spectrum of NaAlSi2O6 jadeite. A quantum mechanical simulation

The Raman spectrum of NaAlSi₂O₆ jadeite is simulated and compared with two recent experimental data sets. In one experiment, only 17 (out of 30 symmetry allowed) peaks and a qualitative estimate of the intensities are provided. In the second case, the digitalized spectrum is available, from which we have been able to extract 20 evident peaks and an estimate of the relative intensities. The present calculation is based on an ab initio quantum mechanical treatment. Using an all‐electron Gaussian‐type basis set, together with the hybrid B3LYP density functional, the full set of 30 active modes and their (polycrystalline and polarized) intensities are obtained. The simulated intensities (not available in a previous study of the same system) permit the two experimental spectra to be reconciled and explain why the missing peaks were not seen. This ultimately leads to excellent agreement between experiment and theory. By artificially varying the mass of the Na ⁺ and Al^{3 +} cations in the simulations, which can be performed automatically and at essentially no computational cost, the vibrational modes to which these ions contribute are identified. We conclude that quantum mechanical simulation can be a very useful complementary tool for the interpretation of experimental Raman spectra. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterisation of human hair surfaces by means of static ToF-SIMS: A comparison between Ga and C60 primary ions

This study deals with the secondary ion yield improvement induced by using C₆₀⁺ primary ions instead of Ga⁺ ones to characterize human hair surfaces by ToF-SIMS. For that purpose, a bunch of hair fibres has been analysed with both ion sources. A high improvement is observed for the detection of amino acids with C₆₀⁺ primary ions as compared to Ga⁺ ions. As an example, a yield enhancement factor greater than 3000 is found for the CNO⁻ peak. A similar gain is observed for the positive secondary ions characteristic of the amino acids. Most of the atomic ions, such as Ca⁺, O⁻ and S⁻, constitute minor peaks with C₆₀⁺ ions while they often dominate the spectrum in the case of Ga⁺ ions. However, with the C₆₀⁺ source, a series of inorganic combination peaks with the elements Ca, S and O are observed in the positive spectra (i.e. HCaSO₄⁺), while they are marginal with the Ga⁺ source. For the mass range beyond 100 m/z and in both polarities, the hair fingerprints are similar with both sources. In average, for a comparable number of primary ions per spectrum, the C₆₀⁺ ion source gives intensities between two and three orders of magnitude higher than the Ga⁺ one.     

Nuclear structure of light nuclei using the selectivity of high energy transfer reactions with heavy ions

We present data obtained by bombarding light nuclei with beams of ¹¹B, ¹²C and ¹⁴N at energies of about 10 MeV/nucleon. Reactions involving transfers of various numbers of nucleons were investigated and the spectra of the detected ions correspond to a wide range of excitation energies in the residual nuclei. The results characteristically show only a few strong peaks in each spectrum and the cross sections exhibit many of the features of direct reactions. We explain the apparent high degree of selectivity in terms of the interplay of reaction mechanisms and the structure of the strongly populated states. Firstly, it is shown that a simple semiclassical model of the reaction process indicates that states of the final nucleus with high spin are greatly favoured. On the other hand, it is demonstrated that the shell-model gives a reasonably complete explanation for the occurence of such high spin states at the appropriate excitation energies. These shell-model states are found to be dominated by configuration with the structure of a multi-nucleon cluster, in the ground state of its internal motion, orbiting the core nucleus so that the centre of mass motion of the cluster carries all the excitation quanta.     

Molecular effect in the formation of the energy spectrum upon the transmission of low-energy hydrogen ions through ultrathin carbon foils

The energy spectra of ions transmitted through ultrathin diamond-like foils irradiated by H⁺, H⁺₂, and H⁺₃ ions with energies from 2 to 12 keV/nucleon are studied. For molecular ions incident on the target with identical velocities, a considerable broadening of the energy spectrum is observed with an increase in the ion mass. The spectrum halfwidth reduced to the identical particle velocity remains constant for each type of incident ion, irrespective of the foil thickness.     

Emission mechanism of radiophotoluminescence in Ag-doped phosphate glass

The objective of this study is to investigate the emission mechanism of radiophotoluminescence (RPL) in the Ag⁺-doped phosphate glass (glass dosimeter), which is now used as individual radiation dosimeter, because the emission mechanism of RPL in glass dosimeter was not fully understood. Optical properties such as optical absorption spectrum, RPL spectrum and change of RPL spectrum as a function of X-ray irradiation dose were measured for commercially available glass dosimeter. In this study, we discuss the emission mechanism of two RPL peaks at 460 nm and 560 nm, based on the fact that electrons and holes produced by X-ray irradiation are trapped at Ag⁺ ions to produce Ag⁰ and Ag²⁺ ions, respectively, when the Ag⁺-doped phosphate glass is exposed to X-ray. We would like to propose the emission mechanism of RPL peaks at 460 nm and 560 nm, concerning with Ag²⁺ and Ag⁰ ions.     

Photoluminescence properties of europium-doped porous silicon nanocomposites

We present new results concerning the photoluminescence properties of europium (Eu³⁺) incorporated in porous silicon (PS) matrix. Eu³⁺ ions were embedded in the matrix by simple impregnation of PS layers in chloride solution of europium. Complete and uniform penetration of Eu³⁺ into the pores is proved from RBS study.The PL spectrum shows the existence of several peaks superposed to the PL band of PS. These peaks are related to level transitions in Eu³⁺. The effect of the ray excitation on the PL shows that energy transfer is not the principal route for radiative recombination.A systematic study of the PL versus annealing temperature was performed. It was found that the optimised PL spectrum is found after annealing at 1000°C. Low-temperature study of the PL shows an important increase of the intensity and a broadness of the peaks due to the appearance of a second crystallographic site.     

Electron impact-induced ionization and dissociation of the freon-12 molecule

An experimental technique is described, and the relative cross sections of the single and dissociative electron-impact ionizations of the freon-12 molecule (CCl₂F₂) in the near-threshold energy range are obtained. The experiment is performed on a device that provides the mass separation and recording of ions with a monopole mass spectrometer. The mass spectrum of the freon-12 molecule is measured at various ionizing-electron energies, and the relative cross sections of dissociative ionization are measured for the most intense ion fragments, including isotope-containing fragments. The threshold dependences of these cross sections are used to determine the appearance potentials of the ion fragments. The isotope shift in the thresh-old appearance energies of ion fragments [C³⁵ClF₂]⁺ and [C³⁷ClF₂]⁺ is measured for the first time.     

High-resolution mass spectra of the residual gas in a metallic vacuum system

The mass spectra of the residual gas in a metallic vacuum chamber of capacity 3 l are studied with an MI-9303 high-resolution magnetic resonance mass spectrometer in the mass range 1–140 u. The experiments are carried out under four evacuation conditions in the pressure range P = 10⁻⁸–10⁻¹⁰ Torr, and almost all the mass peaks forming multiplets are resolved. It is shown that the multiplets with mass numbers M≤80 have, as a rule, a multicomponent structure and hydrogen is the basic component responsible for the total pressure in the chamber irrespective of evacuation conditions. Next in order of intensity in the mass spectra are, CH ₄ ⁺ , H²O⁺, CO⁺, and CO ₂ ⁺ peaks. Other lines in the residual gas spectra are largely due to various C-, H-, N-, and O-based compounds. In addition, the background mass spectrum involves Cl-and F-based compounds and noble gas isotopes. The multiplets with M > 80 often degenerate into a single hydrocarbon line.     

Energy distribution of plasma-assisted electron and ion emission from TGS single crystals

Electron and ion emission accompanying non-thermal plasma processes, produced at the surface of TGS single crystals under driving ac electric field exceeding 10³ V/cm, have been carried out. These plasma-assisted emission of electrons and ions were examined by means of time and energy distribution measurements. The intensity of registered charges (electrons and ions) displayed on the 2 ms time scale are represented by two distinct peaks. Time dependent energy spectrum of charges, detected under our experimental conditions, involves electrons and ions with maximum energy up to 30-40 eV for first peaks and up to 70-80 eV for second one. Additionally, the energy of electrons is focused at about 10-15 eV for first and second peaks and about 60-70 eV for second ones; the ion energy spectrum for both peaks exhibits only distinct low energy maximum focused at about 5-15 eV.     

The energy spectra of secondary ions emitted during ion bombardment

Secondary ion energy spectra have been measured for singly charged ions emitted from targets irradiated with 43 keV A⁺ ions. Targets studied include the 3d transition metals (Sc, Ti, V, Cr, Fe, Ni) Cu and Zn, Zr, Al and Si and the compounds SiO₂, Al₂O₃, NaCl, KCl. Energy spectra were measured in the energy range 1–600 eV. In several cases a peak in the energy spectrum in the region around 200 eV has been found. This is in addition to the usual low energy peaks in the region of 5–10 eV. In many cases the low energy peak was observed to decay steadily with irradiation time or to increase with oxygen pressure. In the case of the cleanest Zn spectrum, only the high energy peak can be detected. The data are discussed in relation to current models of secondary ion emission. We conclude that, in general, elemental metal targets which are clean are characterised by the high energy peak in the secondary ion energy spectrum. The slower ions emitted have been neutralised by electron exchange processes. The low energy peaks in unclean, partially clean, oxide coated or compound targets (NaCl, KCl) arise because the neutralisation of the slower ions is either not as efficient or is not possible. The secondary ion emission model of Blaise and Slodzian could account for the emission of ions from most targets.     

The photoacoustic absorption spectrum of VO2+ ions in cerium orthophoshate

The photoacoustic absorption spectrum of vanadium-doped CePO₄ samples has been observed at room temperature. Two absorption peaks are seen, one at 11200 cm^-1 and another at 14800 cm^-1. They are attributed to VO²⁺ ions in interstitial sites of distorted octahedral symmetry.     

利用红外多光子解离光谱和理论计算揭示由脯氨酸和苯丙氨酸构成的质子化异源二聚体的结构

本文利用傅里叶变换离子回旋质谱仪和红外光学参量振荡器激光器相结合,在2700∽3700 cm^-1范围内获得了由脯氨酸和苯丙氨酸组成的质子化异源二聚体ProPheH⁺的红外多质子解离(IRMPD)光谱. 实验光谱表明,ProPheH⁺除了在3565 cm^-1处有一个对应于自由羧基O$-$H拉伸振动的吸收峰之外,在2935 cm^-1和3195 cm^-1处有两个宽吸收峰. 进一步对ProPheH⁺的结构在M062X/6-311++G(d,p)水平上进行了广泛的理论计算. 结果表明,其能量最稳定的构型具有电荷溶剂化结构,其中质子与脯氨酸单元结合. 这一构型的理论预测光谱与实验谱吻合较好.     

Effect of laser irradiation on the structure and valence states of copper in Cu-phosphate glass by XPS studies

The effect of laser irradiation using three different wavelengths (IR, visible and UV) generated from Nd:YAG laser on the local glass structure as well as on the valence state of the copper ions in copper phosphate glass containing CuO with the nominal composition 0.30(CuO)-(0.70)(P₂O₅), has been investigated by X-ray photoelectron spectroscopy (XPS). The presence of asymmetry and satellite peaks in the Cu 2p spectrum for the unirradiated sample is an indication of the presence of two different valence states, Cu²⁺ and Cu⁺. Hence, the Cu 2p_3/2 spectrum was fitted to two Gaussian-Lorentzian peaks and the corresponding ratio, Cu²⁺/Cu_total, determined from these relative areas clearly shows that copper ions exist predominately (>86%) in the Cu²⁺ state for the unirradiated glass sample under investigation. For the irradiated samples the symmetry and the absence of satellite peaks in the Cu 2p spectra indicate the existence of the copper ions mostly in Cu⁺ state. The O 1s spectra show slight asymmetry for the irradiated as well as unirradiated glass samples which result from two contributions, one from the presence of oxygen atoms in the P-O-P environment (bridging oxygen BO) and the other from oxygen in an P-O-Cu and PO environment (non-bridging oxygen NBO). The ratio of NBO to total oxygen was found to increase with laser power.     

Preparation, characterization and study of optical properties of ZnS nanophosphor

In this work the preparation, characterization and photoluminescence studies of pure and copper-doped ZnS nanophosphors are reported, which are prepared by using solid-state reaction technique at a temperature of 100 °C. The as-obtained samples were characterized by X-ray diffraction (XRD) and UV-VIS Reflectance spectroscopy. The XRD analysis confirms the formation of cubic phase of undoped as well as Cu²⁺-doped ZnS nanoparticles. Furthermore it shows that the average size of pure as well as copper-doped samples ranges from 15 to 50 nm. The room-temperature PL spectra of the undoped ZnS sample showed two main peaks centered at around 421 and 450 nm, which are the characteristic emissions of interstitial zinc and sulfur vacancies, respectively. The PL of the doped sample showed a broad-band emission spectrum centered at 465 nm accompanied with shoulders at around 425, 450 and 510 nm, which are the characteristic emission peaks of interstitial zinc, sulfur vacancies and Cu²⁺ ions, respectively. Our experimental results indicate that the PL spectrum confirms the presence of Cu²⁺ ions in the ZnS nanoparticles as expected.     

Spectroscopic properties of alexandrite crystals II

Several aspects of the optical spectroscopic properties of alexandrite crystals not previously investigated are reported here. For Cr³⁺ ions occupying the Al³⁺ lattice sites with mirror symmetry in BeAl₂O₄, the positions of the zero-phonon lines for absorption transitions to the ²T_1g and ⁴T_2g levels are identified, and vibronic transition peaks in the fluorescence spectrum are compared to transitions appearing in the Raman spectrum and Stokes excitation spectrum. In addition, the effects of radiation trapping are shown to lengthen the fluorescence lifetime of the ²E_g - ⁴A_2g transition for ions in these sites at low temperatures. For Cr³⁺ ions occupying the Al³⁺ lattice with inversion symmetry, the ground state splitting of the ²E_g - ⁴A_2g transition is reported and the decrease of the fluorescence lifetime with temperature is shown to be due to the increase in vibronic emission probability as well as increased probability of direct radiationless decay.     

An aes study of a copper-iron sulphide mineral

Synthetic bornite, Cu₅FeS⁴ has been studied by Auger electron spectroscopy. Sputtercleaned bornite shows a sulphur spectrum with three peaks at 138, 147 and 149 eV. These Auger transitions are different from those observed when sulphur is adsorbed on metal surfaces, where the peaks are at 139, 149 and 154 eV. The adsorption of oxygen on the surface of bornite at room temperature results in the formation of a layer of iron oxide and, in addition, the sulphur spectrum loses its fine structure and shows only a single peak at 148 eV. Under the influence of both the ion sputter beam and the electron beam, the surface composition of bornite shows large and rapid changes which are due mainly to movement of mobile Cu⁺ ions through the lattice, this movement being caused by surface charging effects.     

Cosmic ray spectrum obtained from the energy scattered by the particles of extensive air showers in the atmosphere and the galactic model

The differential energy spectrum of cosmic rays that is obtained on the basis of the measurements of Cherenkov radiation from extensive air showers in an energy range of 10¹⁵–10²⁰ eV is compared with the model of the propagation of primary particles in the interstellar medium with fractal properties. It is found that the shape of the experimental spectrum is in good agreement with the shape of the calculated spectrum of “all particles” at 10¹⁵–10¹⁸ eV. The average mass composition of cosmic rays that is calculated on the basis of five components does not contradict the average mass composition obtained from the experimental data for several parameters in this energy range.     

Evidence for Potassium-Sucrose Interaction in Biological Mid-Infrared Spectra by Multidimensional Analysis

Complex-formation between carbohydrates and cations could have important biological implications.

In this work, Mid-Infrared spectra of pure sucrose solutions and of biological solutions containing sucrose and potassium ions (K+) were investigated by Principal Component Analysis (PGA).

By direct examination of the Mid-Infrared spectra of the biological solutions containing K⁺ ions, no interactions between the cations and sucrose molecules could be observed. However, when the spectral pattern obtained by PCA and which is associated with sucrose, was examined, splitting and shifts in the characteristic absorption bands were observed owing to interactions between sucrose molecules and K⁺ ions. The 997 cm-1 peak which had a visible shoulder at 991 cm-1 and that is observed in pure solutions, was decomposed in the biological solutions into 3 distinct peaks at 1004, 996 and 990 cm-1. The two peaks centered at 1053 cm-1 were split into 3 peaks: 1060, 1051, 1045 cm-1. Hence by PCA, shoulders were characterized in biological solutions and more distinct peaks could be observed. These split and shift phenomena are similar to those obtained when crystalline sugar salts were investigated. This type of interaction, involving potassium ions and sucrose molecules, would be responsible for the storage of this cation which role is essential in plant metabolism.     

Interpretation of secondary ion mass spectra by means of fingerprint spectra and secondary ion imaging

A passive layer, of several thousand ? thickness, formed on a polycrystalline nickel electrode, has been examined using secondary ion mass spectrometry (SIMS) by spottering with a 5.5 keV, 13μA·cm⁻²,⁴⁰Ar⁺ primary beam. Concentration profiles were detived by monitoring the intensities of atomic and molecular mass peaks as a function of sputtering time (i.e. depth). Nickel was present throughout the layer but not as the element since the relative intensities of the Ni _n ⁺ (n=1, 2, 3, 4) peaks, constituting part of its fingerprint spectrum, differed from those in the fingerprint spectrum of elemental nickel. These values were eventually reached, signifying piercing of the layer and thus providing a means of estimating its thickness. Imaging of⁵⁸Ni⁺ showed the presence of nickel in at least two different modifications in the layer, both with higher Ni⁺ yields than the bulk nickel. Their fractional coverages were estimated from the images taken at various depths. The resulting profile of the Ni⁺ originating from one of these modifications was found to be proportional to the¹⁶O⁻ profile, indicating that these ions originate from the same molecule. This example demonstrates the advantage of combining different SIMS modes (viz. depth profiles, fingerprint spectra and imaging) in tackling certain analytical problems.     

Local structure analysis of YSZ by Y-89 MAS-NMR

The local coordination structure around Yttrium ions in yttria stabilized zirconia (YSZ) has been investigated by ⁸⁹Y MAS-NMR. The NMR spectrum showed multiple peaks corresponding to yttrium ions in different coordination numbers. The compositional dependence of spectra was observed. Yttrium ions of different oxygen coordination number were quantified. The oxygen vacancy concentration around the cations was determined. It was found that the vacancies were distributed around Zirconium ions in lower Y₂O₃ concentrations, and the vacancy concentration located to Yttrium began increasing at concentrations above 10 mol% Y₂O₃. The local structure change was able to be directly observed by ⁸⁹Y NMR measurements.