Ion Emission Intensity Research Articles

Experimental study on the full cycle evolution of high-intensity atmospheric dc arc discharge from breakdown to extinguishment.

In this study, the spatiotemporal evolution of full cycle of high-intensity dc argon arc discharge at atmospheric pressure is investigated by using a transferred arc device, which is easy to be directly observed in the experiment. Combining the voltage and current waveforms with high-speed images, the full cycle evolution process of high-intensity atmospheric dc arc can be divided into five different stages: breakdown pulse stage, cathode heating stage, current climbing stage, stable arc discharge stage, and finally arc extinguishing stage. The characteristics of each different stage are analyzed in detail through the electrical properties, high-speed pictures, and spectroscopic measurements. The results show that the strong luminescence region develops from the vicinity of cathode and anode to the middle in the breakdown pulse stage, which is explained from the spatiotemporal evolution of distributions of excited argon atom and ions. The development velocity of emission intensity of argon ions is mainly determined by the dominant stepwise ionization process. Then the cathode heating stage appears with many bright and nonuniformly distributed light spots on the cathode surface, and the electron emission mechanism of cathode gradually changes to the thermionic emission as the surface temperature rises. With the increase of arc current, the discharge channel significantly expands, then becomes stable due to the increment of the Lorentz force. The characteristics of arc extinguishing stage are clarified in terms of the decay of charged particles density.

Color tunability studies of samarium ions/silver nanoparticles doped titanosilicate glass matrix

The current study aims at synthesizing a titanosilicate glass composite doped with rare earth/plasmonic nanoparticles using a cost effective and easier method of non-hydrolytic sol gel method. The rare earth employed is samarium ions while the plasmonic nanoparticle used is Silver. For densification samples were annealed at 800 0C and further characterized by FTIR, XRD, TEM. Matrix confirmation is done by FTIR spectroscopic studies which confirm the presence of Si-O-Si, Si-O, and Ti-O-Ti bonds. Both XRD and TEM analysis affirm the presence and morphology of Ag and TiO2 nanoparticles respectively. In the photoluminescence analysis the trivalent samarium ions show strong reddish-orange luminescence in the 550–670 nm range. The major peaks are obtained at 581 nm, 662 nm, 605 nm. Each of the spectra obtained show three prominent characteristic emission bands correlated to the transitions 4G5/2 to 6H5/2, corresponding to 581 nm, 4G5/2 to 6H7/2 corresponding to 605 nm, and 4G5/2 to 6H9/2 corresponding to 662 nm. We successfully plotted the CIE colorimetry diagram and it is observed that the effect of plasmonic nanoparticles can tune the relative emission intensity of rare earth ions in CIE colorimetry. Our study highlights the significance of incorporating the rare earth ions doping with plasmonic nanoparticles in the color tunability studies, exhibiting their broad applications in LED devices.

SIMS studies of hydrogen interaction with the TiFe alloy surface: hydrogen influence on secondary ion yields

Secondary ion mass spectrometry is a powerful analytical tool that offers great capabilities for studying hydrogen interaction with metallic materials. Yet its utilization for the in situ studies of hydrogen interaction with a sample has not been well established. In this research we study the influence of hydrogen partial pressure (5 × 10−9 – 5 × 10−5 Torr) in the sample chamber, the sample temperature (305–900K), and primary ion current density on the emission intensity of various secondary ions for the hydrogen-storage TiFe alloy sample bombarded with 12 or 20 keV Ar+ primary ions. Presence of chemisorbed hydrogen on the alloy surface results in the presence of a variety of positive and negative hydrogen-containing secondary ions in mass spectra. Analysis of the influence of the varied experimental parameters has shown that the secondary ion yield changes reflect only changes of hydrogen concentration regardless of which varied parameter induced a concentration change. The yield dependences on concentration in general are different for different ions and tend to be more substantial for the ions containing a larger number of hydrogen atoms. The ions containing one hydrogen atom have similar and likely linear yield dependences when the concentration is low. At higher concentrations, the yield dependences for these ions diverge: their relation to concentration is discussed. For not hydrogen-containing secondary ions, hydrogen saturation of the surface resulted in an 80-400% increase of the yields of Ti+ and Ti-containing positive secondary ions, no yield change for other positive ions, and 2–3-times decrease of yields of negative ions. As for hydrogen interaction processes with the alloy surface, the obtained dependence of the ion yields only on hydrogen concentration indicates that the alloy surface is rather homogeneous i.e. without large parts that have different characteristics of interaction with hydrogen and different ratios of secondary ion yields. The results of the sample temperature influence indicate that the chemisorption probability of hydrogen molecules is temperature independent at least in the ∼300-500 K range. The substantial decrease in concentration at temperatures above 450 K is a result of associative desorption of hydrogen, although a possible contribution of other processes is not excluded by the presented results.

Sputtering of Oxides from LaNi5 Surface

The changes in chemical composition of the intermetallic alloy LaNi5 surface monolayers were studied using secondary ion mass spectrometry (SIMS) in the process of the alloy interaction with oxygen. The investigated samples were pellets made by pressing the fine-grained LaNi5 alloy. Ar+ ions having energies of 10-18 keV were used as primary ions. The primary beam current density was 9-17 μA·cm-2, which corresponds to the dynamic SIMS mode. The emission intensities of secondary ions were measured within the dynamic range of at least 6 orders of magnitude. Before the measurements, the samples were annealed in residual vacuum at a temperature of ~ 1000 K. After the annealing, the sample surface was cleaned using the primary ion beam until the mass-spectrum composition and secondary ion emission intensity stabilized completely. The gas phase composition was monitored using a gas mass spectrometer. The conducted studies showed that a complex chemical structure including oxygen, lanthanum, and nickel is formed on the surface and in the near-surface region of LaNi5 as a result of its exposure to oxygen. Oxygen forms strong chemical bonds in such a structure with both components of the alloy. This is evidenced by the presence of a large set of oxygen containing emissions of positive and negative secondary ions with lanthanum, with nickel, and oxygen containing lanthanum-nickel cluster secondary ions in mass spectra. The resulting oxide compounds have a bulk structure and occupy dozens of monolayers. In such a bulk oxide structure, the outer monolayers are characterized by the highest ratio of oxygen atom number to the number of matrix atoms. This ratio decreases along the transition from the surface to the underlying monolayers. This process occurs uniformly, without any phase transformation. The observed secondary ions are not a product of association between sputtered surface fragments and oxygen in the gas phase at the fly-off stage after sputter-ejection, but they are products of the oxide compounds being sputtered, hence they characterize the composition of surface and near-surface region.

Study of optical interaction between UO2++ and Ho3+ in zinc phosphate glass

A study of Non-radiative energy transfer in UO2-Ho system in zinc phosphate glass has been done by observing the steady state emission of UO2++ with varying concentration of Ho3+ in zinc phosphate glass at room temperature. It has been observed that UO2++ ion emission intensity decreases with increasing Ho3+ concentration resulting in a non-radiative energy transfer from UO2++ to Ho3+. The energy transfer mechanism for the systems is confirmed to be electric dipole-dipole in nature according to Fong-Diestler’s, Forster and Dexter’s and Van Uitert’s theory. The donor-acceptor distances (DD→A) and transfer efficiencies (η), as well as energy transfer probabilities (Pda) in presence of different acceptor concentration, have been calculated.

A physico-chemical model to study the ion density distribution in the inner coma of comet C/2016 R2 (Pan-STARRS)

ABSTRACT The recent observations show that comet C/2016 R2 (Pan-Starrs) has a unique and peculiar composition when compared with several other comets observed at 2.8 au heliocentric distance. Assuming solar resonance fluorescence is the only excitation source, the observed ionic emission intensity ratios are used to constrain the corresponding neutral abundances in this comet. We developed a physico-chemical model to study the ion density distribution in the inner coma of this comet by accounting for photon and electron impact ionization of neutrals, charge exchange and proton transfer reactions between ions and neutrals, and electron–ion thermal recombination reactions. Our calculations show that CO2+ and CO+ are the major ions in the inner coma, and close to the surface of nucleus CH3OH+, CH3OH2+, and O2+ are also important ions. By considering various excitation sources, we also studied the emission mechanisms of different excited states of CO+, CO2+, N2+, and H2O+. We found that the photon and electron impact ionization and excitation of corresponding neutrals significantly contribute to the observed ionic emissions for radial distances smaller than 300 km and at larger distances, solar resonance fluorescence is the major excitation source. Our modelled ion emission intensity ratios are consistent with the ground-based observations. Based on the modelled emission processes, we suggest that the observed ion emission intensity ratios can be used to derive the neutral composition in the cometary coma only when the ion densities are significantly controlled by photon and photoelectron impact ionization of neutrals rather than by the ion–neutral chemistry.

Enhancement of Eu3+ photoluminescence in sodium-aluminosilicate glasses by silver molecular clusters formed with Na+-Ag+ ion exchange method

Subject of Research. The paper considers the interaction of silver molecular clusters with trivalent europium ions in ion- exchanged layers of sodium-aluminosilicate glasses. Method. Glasses based on Na2O–ZnO–Al2O3–SiO2–F system anddoped with Sb2O3 and Eu2О3 were synthesized for the study. Silver ions were introduced into the synthesized glasses by low-temperature Na+–Ag+ ion exchange method; glass samples were immersed in a bath containing a melt of nitrate mixture 5AgNO3/95NaNO3 (mol%) at 320 °C for 15 minutes. To promote the growth of silver molecular clusters in ion-exchanged samples they were heat-treated at 350–450 °С for 20 hours. Heat treatment temperature was 500 °С for obtaining silver nanoparticles in the samples. Main Results. We have studied the spectral-luminescent properties of sodium-aluminosilicate glasses doped with silver molecular clusters and trivalent europium ions in ion-exchanged layers. Luminescence intensity of Eu3+ ions in the ion-exchanged glass with silver molecular clusters was found out to exceed considerably the intensity in the as-synthesized glass. Glass samples heat-treated at 450 °С are characterized by maximal emission intensity of silver molecular clusters and europium ions. Quenching of the luminescence was observed for the samples containing silver nanoparticles. Practical Relevance. Obtained results can be applied for developing phosphors in glass for LEDs and down-converters of ultraviolet radiation for solar cells

Effect of the RF power on the characteristic properties of high-performance silicon nitride single-layer permeation barriers

Permeation barriers for organic devices and packaging on flexible substrates are realized by using a simple single-layered silicon nitride (SiNx) film deposited via radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) at a low temperature (~70 °C) with plasma and radical control. Several operation parameters like RF power and treatment time duration were changed to study the impact of plasma parameters (electron excitation temperature, atomic N radical and N+ ions) on the barrier films. Optical emission spectroscopy (OES) diagnostic is used to explore the deposition conditions to improve the quality and the properties of the permeation barriers deposited on a polyethylene terephthalate (PET) substrate. OES measurements revealed that the minimum electron excitation temperature and high intensity of the N+ ion observed by an 870.2 nm emission line were the crucial parameters to achieve the minimum water vapor transmission rate (WVTR) by changing the film microstructure factor with all other operation parameters remained fixed. By incorporating plasma and radical treatment at different RF powers, a minimum WVTR of 1.8 × 10−2 g/m2/day, measured at room temperature was achieved relevant to the condition of the maximum N+ ion emission intensity. The decrease in permeability is attributed to the rearrangement of the atoms at the interfaces when the average transferred ion energy to the substrate exceeds the threshold of displacement energy = electron excitation temperature ~ electron temperature. Also, this work reports on the correlations between the plasma chemistry and the chemical, mechanical, barrier, and optical properties of the deposited films.

Hollow tubular Tb3+and Yb3+ co-doped ordered mesoporous ZnO composite materials and its luminescent properties

In this study, a much regular hollow tubular ordered porous structure (Tb3+-Yb3+) SSA/ZnO composite was prepared by hydrothermal method. In the prepared process, an ordered porous zinc oxide was necessarily used as precursor which was prepared by soft template method. The sulfosalicylic acid was used as an organic ligand to provide energy for the energy level transfer of rare earths, which also showed the effect of the structure-directing agent for the structure. Yb3+ acted as a sensitizer which enhanced the luminescent intensity of Tb. Tb3+ was the luminescent center, it also acted a part of the mineralizer which influenced the morphology of samples. The sample showed a special hollow tubular structure which was assembled from many nanoparticles, and there were the ordered pores in the particles. The sample showed the emission peak at 489, 543, 585 and 620 nm, and the highest emission peak located at 543 nm. The optimum doping ratio of Tb3+ and Yb3+ was determined by the difference in fluorescence intensity. The porous ZnO promoted the emission intensity of rare earth ions, and greatly reduced the use of rare earth.

Correlation between plasma glow intensity distribution and sputtering profile in dc magnetron discharge

The correlation between the plasma glow intensity distribution and the target sputtering profile in an axially symmetric unbalanced dc magnetron discharge with copper cathode in argon is studied. At high pressures the argon atom and ion emission intensities are in good agreement with a sputtering profile. In case of low pressures, a satisfactory agreement is only for the ion emission. The best estimates of the sputtering profile can be obtained from the argon ion emission distribution at not too low pressures.

Report on cascade energy relaxation from PVP to Tb3+:Bi2SiO5 nanophosphor through salicylic acid in composite polymeric film

The present article reports structural and spectroscopic properties of Tb:Bi2SiO5 nanophosphors dispersed in Polyvinylpyrrolidone polymer film, in presence of Salicylic acid (SA) molecule, which acts as a sensitizer. Detailed structural and spectroscopic characterizations were carried out using X-ray diffraction patterns, Scanning Electron Microscope, Fourier Transform Infrared and Excitation and photoluminescence techniques. The mean crystallite size of Tb3+:Bi2SiO5 nanophosphor and Tb3+:Bi2SiO5 in Polyvinylpyrrolidone polymer composite was estimated ∼22 nm and ∼28 nm, respectively. We have report atleast two times enhancement in Tb3+ ions emission intensity due to the efficient energy transfer from salicylic acid molecule to Tb ions. In addition to energy transfer from salicylic acid, the Polyvinylpyrrolidone polymeric host was also reported to serve as a sensitizer for SA molecule and Tb3+ ions through a cascade energy relaxation process while exciting with 248 nm photons. On 248 nm photon excitation, atleast five improvements in Tb3+ ion emission intensity are reported. Presence of SA molecule facilitates precise colour tuning as obvious from the CIE coordinates.

Experimental study of atmospheric-pressure micro-plasmas for the ambient sampling of conductive materials

Conductive solid material sampling by micro-plasma under ambient atmosphere was studied experimentally. A high-voltage pulse generator was utilized to drive discharge between a tungsten needle and metal samples. The effects of pulse width on discharge, micro-plasma and sampling were investigated. The electrical results show that two discharge current pulses can be formed in one voltage pulse. The duration of the first current pulse is of the order of 100 ns. The duration of the second current pulse depends on the width of the voltage pulse. The electrical results also show that arc micro-plasma was generated during both current pulses. The results of the emission spectra of different sampled materials indicate that the relative emission intensity of elemental metal ions will increase with pulse width. The excitation temperature and electron density of the arc micro-plasmas increase with the voltage pulse width, which contributes to the increase of relative emission intensity of metal ions. The optical images and energy dispersive spectroscopy results of the sampling spots on metal surfaces indicate that discharge with a short voltage pulse can generate a small sputtering crater.

Structural and photophysical investigations of bright yellow emitting Dy: ZnAl2O4 nanophosphor

ZnAl2O4:Dy nanophosphors were synthesized using co-precipitation and hydrothermal methods. Various structural and optical characterizations were made using X-ray diffraction (XRD), Transmission electron microscopy, Scanning electron microscopy, UV-Visible absorption, Infrared absorption, photoluminescence and time resolved luminescence techniques. Dy3+ doped samples showed yellow dominating multicolour emission on excitation with 348nm. We have estimated J–O parameters and other various radiative parameters like quantum efficiency, Stimulated emission cross-section etc. Considerable effect of SiO2 was noticed on crystalline size and emission intensity of Dy ions. A comparison between the samples synthesized by different methods, and Dy concentration has been made and detail report presented in the article.

Experimental evidence for quantum cutting co-operative energy transfer process in Pr3+/Yb3+ ions co-doped fluorotellurite glass: dispute over energy transfer mechanism.

Pr3+/Yb3+ doped materials have been widely reported as quantum-cutting materials in recent times. However, the question of the energy transfer mechanism in the Pr3+/Yb3+ pair in light of the quantum-cutting phenomenon still remains unanswered. In view of that, we explored a series of Pr3+/Yb3+ co-doped low phonon fluorotellurite glass systems to estimate the probability of different energy transfer mechanisms. Indeed, a novel and simple way to predict the probability of the proper energy transfer mechanism in the Pr3+/Yb3+ pair is possible by considering the donor Pr3+ ion emission intensities and the relative ratio dependence in the presence of acceptor Yb3+ ions. Moreover, the observed results are very much in accordance with other estimated results that support the quantum-cutting phenomena in Pr3+/Yb3+ pairs, such as sub-linear power dependence of Yb3+ NIR emission upon visible ∼450 nm laser excitation, integrated area of the donor Pr3+ ion's visible excitation spectrum recorded by monitoring the acceptor Yb3+ ion's NIR emission, and the experimentally obtained absolute quantum yield values using an integrating sphere setup. Our results give a simple way of estimating the probability of an energy transfer mechanism and the factors to be considered, particularly for the Pr3+/Yb3+ pair.

Sensitization enhancement of europium in ZnSe/ZnS core/shell quantum dots induced by efficient energy transfer.

Eu-doped ZnSe:/ZnS quantum dots (formed as ZnSe:Eu/ZnS QDs) were successfully synthesized by a two-step wet chemical method: nucleation doping and epitaxial shell growing. The sensitization characteristics of Eu-doped ZnSe and ZnSe/ZnS core/shell QD are studied in detail using photoluminescence (PL), PL excitation spectra (PLE) and time-resolved PL spectroscopy. The emission intensity of Eu ions is enhanced and that of ZnSe QDs is decreased, implying that energy was transferred from the excited ZnSe host materials (the donor) to the doped Eu ions (the acceptor). PLE reveals that the ZnSe QDs act as an antenna for the sensitization of Eu ions through an energy transfer process. The dynamics of ZnSe:Eu/ZnS core/shell quantum dots with different shell thicknesses and doping concentrations are studied via PL spectra and fluorescence lifetime spectra. The maximum phosphorescence efficiency is obtained when the doping concentration of Eu is approximately 6% and the sample showed strong white light under ultraviolet lamp illumination. By surface modification with ZnS shell layer, the intensity of Eu-related PL emission is increased approximately three times compared with that of pure ZnSe:Eu QDs. The emission intensity and wavelength of ZnSe:Eu/ZnS core/shell quantum dots can be modulated by different shell thickness and doping concentration. The results provide a valuable insight into the doping control for practical applications in laser, light-emitting diodes and in the field of biotechnology.

Co-luminescence properties of terbium ions–benzoic acid–phen complexes doped with europium ions

Series of complexes Eu x Tb1−x (BA)3phen (0.01 ≤ x ≤ 0.50) were synthesized by co-precipitation method, BA was used as the carboxylic acid ligand and 1, 10-phenanthroline was used as the electrically neutral ligand. The samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analyses and differential scanning calorimetry (TG–DSC), ultraviolet and visible spectrophotometer absorption spectra, and photoluminescence spectra to study the structure, the energy absorption, the thermal, and luminescent properties of the rare earth complexes. The results show that the series rare earth organic complexes are well crystallized and show high thermal stability. The luminescent intensity of europium ion in the complexes increases as terbium ion transfers the absorbed energy to europium ion in the complexes. The emission of terbium ion at 545 nm is not quenched by europium ion but increases with the content of europium ion decreasing. When the x value is 0.01, the fluorescence intensity reaches the maximum as well as the emission intensity of terbium ions at 545 nm and europium ions at 614 nm are almost equal. It realizes the co-luminescence phenomenon of terbium ion and europium ion. The series rare earth organic complexes with different colors can be obtained by adjusting the ratio of terbium ion and europium ion.

Synthesis and characterisation of folic acid based lanthanide ion probes

As a first step in the process of developing folate based visual probes and contrast agents, we have designed and synthesised a series of first generation lanthanide(III) molecular probes. The molecular probe structure included a lanthanide(III) (Eu(III), Tb(III), Gd(III)) chelate which was linked (2 or 3) to either a folic acid or pteroic acid targeting motif. We have defined the emission properties of the molecular probes at different pHs, the emission lifetimes, and the number of metal bound water molecules. The cellular uptake of the molecular probes was investigated in HeLa cells and the amount of Eu(III) internalisation quantified by inductively coupled plasma mass spectrometry. Our results highlighted several key features of probe design: a shorter linker was more optimal for both Eu(III) ion emission intensity and cellular uptake; the folic acid targeting motif exhibited higher cellular uptake when compared to pteroic acid; the emission intensity of the folic acid based probes was pH insensitive, whereas the pteroic acid based probes were pH sensitive. These first generation folate molecular probes displayed promising chemical and physical properties, suggesting that optical and MRI probes can potentially be developed, to enable the imaging of folate receptors in cancer cells and tissues.

Eu3+ luminescence in aluminophosphate glasses

With a 4f6 electronic configuration, europium ions in the trivalent charge state are known to be efficient activators in wide band gap matrices. Embedded in the aluminophosphate (Li2O–BaO–Al2O3–La2O3–P2O5) glasses the optically activated Eu3+ ions lead to intense room temperature orange/red luminescence with 16–23Cd/m2 by using ultraviolet pumping. The as-prepared and heat treated europium doped glasses for temperatures below and above Tg were studied by room temperature Raman spectroscopy, absorption, photoluminescence excitation, temperature dependent and time dependent photoluminescence. When the samples are excited by 325nm wavelength photons, an enhancement of the red luminescence intensity by ca. one order of magnitude was found to occur for temperatures between 14K and 350K, for all the doped glasses. On the other hand, by using resonant excitation on the 5L6 Eu3+ excited state (λexc~390nm) the ion emission intensity was found to be nearly constant for temperatures up to 500K. For higher temperatures a steeper decrease of the luminescence intensity occurs due to non-radiative competitive channels described by activation energies of ca. 235meV and 450meV by using 325 and 390nm wavelength photons as excitation, respectively. The lifetime of the 5D0 level in these glasses is ca. 2.93ms. A discussion of the thermal population and de-excitation mechanisms is performed.

Spectroscopic properties of Er3+ and Ce3+ co-doped tellurite glasses

Optical absorption, near infrared emission and FTIR studies were carried out for the glasses prepared with chemical composition of (61.5−x)TeO2+25ZnO+8K2O+5CaO+0.5Er2O3+xCe2O3 (TZKCEr05Cex; x=0, 0.1, 0.5, 1.0mol%) by the conventional melt quenching technique. Judd–Ofelt analysis has been adopted for the experimental oscillator strengths of the absorption bands of 0.5mol% of Er3+ ions in singly doped TZKC glass. From the Judd–Ofelt intensity parameters (Ωλ), different radiative parameters were evaluated and the effect of Ce3+ ions concentration on the Er3+ ion emission intensities of 4I13/2→4I15/2 transition has been discussed.

Inside Cover: Rare-Earth Nanoparticles with Enhanced Upconversion Emission and Suppressed Rare-Earth-Ion Leakage (Chem. Eur. J. 18/2012)

Rare-earth nanoparticles (NPs) with upconversion (UC) emission have attracted much attention for their potential applications in bioimaging. The image shows a small, heterogeneous, core/shell nanostructure, NaYF4:Yb,Er@CaF2 NPs, with highly enhanced UC emission intensity and low leakage of rare-earth ions, ensuring safe bioprobes. The background shows cell imaging demonstrated with these NPs. For more details see the Full Paper by L.-D. Sun, C.-H. Yan et al. on page 5558 ff.