Visible Emission Lines Research Articles

Observation of Nd3+ visible line emission in ZnO : Nd3+ prepared by a controlled reaction in the solid state

Visible emission from ZnO is usually broadband and realizing line emission from rare earth f–f transitions in ZnO at room temperature has proven to be difficult. A controlled solid-state reaction process with different standing times to synthesize rare earth doped (Nd3+) zinc oxide (ZnO) has shown that sharp and intense line emission in the orange region (595 nm) could be realized under blue excitation, where both excitation and emission transitions occur between Nd3+ levels situated intragap in ZnO. In addition, host-to-Nd3+ energy transfer is also observed under band-to-band excitation. Incidentally, undoped ZnO synthesized by an identical process exhibits a broad green emission. Detailed characterization of the ZnO :Nd3+ powder by x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, x-ray photoelectron spectroscopy, photoluminescence spectroscopy and time-resolved decay indicates a hexagonal phase with the presence of Nd3+ in the ZnO lattice, forming spherical particles (∼200 nm) having a sharp visible emission with decay time in the microsecond range (9.60 µs).

Visible emission line space solar coronagraph: science and optical design

A solar coronagraph above the Earth’s atmosphere provides ideal conditions to study various properties of coronal plasma such as pressure, density, and temperature perturbation leading to the existence of waves, the topology of magnetic fields, dynamical nature of coronal loops & CME’s and space weather predictions. Keeping in view of these scientific objectives of coronal dynamics, a 20 cm coronagraph is being planned to be launched in space by ISRO. The solar corona will be imaged in two bright coronal emission lines (viz., the green and the red-lines at 530.3 nm and 637.4 nm respectively). The field-of-view (FOV) of interest in the solar corona is from 1.05 to 3.0 solar radii in order to maximize the science outcome of coronal dynamics and also to provide complementary data to the other existing/planned space missions. The optical design of the coronagraph has a 20-cm diameter off-axis parabolic mirror as its main optical imager. The mirror has a stringent requirement of 0.1–0.15 nm micro-roughness in order to provide a scatter light of less than 5-ppm. This mirror and other reflecting optics required for the coronagraph are being fabricated at LEOS, ISAC. The full optical design is optimized for the diffraction-limited imaging capabilities and is discussed in this paper along with the scientific objectives of the payload.

Extreme Ultraviolet (EUV) Emission Measurement from a Coaxially Focused Plasma for Various Pressures of an Argon and Ne-Xe Gas Mixture

Ar and Ne-Xe (30%) plasmas were generated in a dense plasma-focus device with coaxial electrodes extreme ultraviolet (EUV) lithography. The EUV intensity and the electron temperature were investigated. An input voltage of 4.5 kV was applied to a capacitor bank of 1.53 µF, and the diode chamber was filled with Ar and Ne-Xe (30%) gas at a prescribed pressure. The inner surface of the cylindrical cathode was lined with an acetal insulator. The anode was made of tin metal. The EUV emission signal with a wavelength in the range of 6 16 nm was detected by using a photo-detector (AXUV-100 Zr/C, IRD). The visible emission line was detected by using a composite-grating spectrometer with a working wavelength range of 200 1100 nm (HR 4000CG). The electron temperature could be obtained from optical emission spectroscopy (OES) and was determined by using a Boltzmann plot under the assumption of local thermodynamic equilibrium (LTE).

Spectroscopic Diagnostic of Helium-Hydrogen RF Plasma under the Influence of Radiation Trapping

The electron temperature and density, atomic hydrogen density and temperature in a helium-hydrogen RF plasma are determined from the visible emission line intensities of both atoms by considering photoexcitation from the ground state accompanied by radiation trapping in the plasma. From the observed helium line intensity, and the hydrogen Balmer γ line intensity which is little affected by photoexcitation, parameters other than the atomic hydrogen temperature are determined using a helium atom collisional-radiative model [Sawada et al., Plasma Fusion Res. 5, 001 (2010)], which includes photoexcitation for helium singlet P states, and a hydrogen atom collisional-radiative model in which photoexcitation is ignored. The atomic hydrogen temperature is determined to reproduce the Balmer α and β line intensities by using an iterative hydrogen atom collisional-radiative model [Sawada, J. Plasma Phys. 72, 1025 (2006)] that calculates the photoexcitation rates.

Collisional-Radiative Model for Spectroscopic Diagnostic of Optically Thick Helium Plasma

We have included the effect of radiation trapping in a collisional-radiative model of neutral helium atoms developed by Goto [M. Goto, JQSRT 76, 331 (2003)], which is used to determine the electron temperature and density in plasmas from visible emission line intensities of atoms. In addition to the electron temperature and density, photo-excitation events from the ground state 11S to the 21P, 31P, and 41P states per second per one atom are treated as fitting parameters to reproduce the population density obtained by spectroscopic measurement. The model has been applied to an RF plasma at Shinshu University, Japan. The electron temperature and density and the contribution of radiation trapping to the population density of excited states are evaluated.

Measurements of spatial line emission profiles in the main scrape-off layer of the DIII-D tokamak

A video camera system is described as that measures the spatial distribution of visible line emission emitted from the main scrape-off layer (SOL) of plasmas in the DIII-D tokamak. A wide-angle lens installed on an equatorial port and an in-vessel mirror, which intercepts part of the lens' view, provide simultaneous tangential views of the SOL on the low-field and high-field sides of the plasma's equatorial plane. Tomographic reconstruction techniques are used to calculate the two-dimensional (2D) poloidal profiles from the raw data, and one-dimensional (1D) poloidal profiles simulating chordal views of other optical diagnostics from the 2D profiles. The 2D profiles can be compared with SOL plasma simulations; the 1D profiles with measurements from spectroscopic diagnostics. Sample results are presented, which elucidate carbon transport in plasmas with toroidally uniform injection of methane and argon transport in disruption mitigation experiments with massive gas jet injection.

Design status of ITER visible/IR outer strike point view

For ITER visible/IR imaging of the outer strike point from the six upper ports currently assigned, we show an optical design that provides a 4 mm Airy disk at 5 μm wavelength at the farthest point in the field of view (much smaller in the visible), with as complete toroidal coverage of the vertical target as possible. Plasma and optical effects provide fundamental limits on the performance and design of the system. Some effects involve interactions of the surfaces with the plasma, such as plasma transport and deposition of material on the surfaces to be viewed, plasma damage to those surfaces, and molecular emission by the plasma at IR wavelengths. We discuss a detailed optical design including the endoscope concept, entrance aperture and collection head, relay optics, and camera specifications and performance. We assess integration times for capture of IR emission from surfaces and visible line emission predicted by boundary modeling.

Shaping planetary nebulae by light jets

We conduct numerical simulations of axisymmetrical jets expanding into a spherical AGB slow wind. The three-dimensional flow is simulated with an axially symmetric numerical code. We concentrate on jets that are active for a relatively short time. Our results strengthen other studies that show that jets can account for many morphological features observed in planetary nebulae (PNs). Our main results are as follows. (1) With a single jet's launching episode we can reproduce a lobe structure having a `front-lobe', i.e., a small bulge on the front of the main lobe, such as that in the PN Mz~3. (2) In some runs dense clumps are formed along the symmetry axis, such as those observed in the pre-PN M1-92. (3) The mass loss history of the slow wind has a profound influence on the PN structure. (4) A dense expanding torus (ring; disk) is formed in most of our runs. The torus is formed from the inflated lobes, and not from a separate equatorial mass loss episode. (5) The torus and lobes are formed at the same time and from the same mass loss rate episode. However, when the slow wind density is steep enough, the ratio of the distance divided by the radial velocity is larger for regions closer to the equatorial plane than for regions closer to the symmetry axis. (6) With the short jet-active phase a linear relation between distance and expansion velocity is obtained in many cases. (7) Regions at the front of the lobe are moving sufficiently fast to excite some visible emission lines.

The Distribution of Active Galactic Nuclei in Clusters of Galaxies

We present a study of the distribution of AGNs in clusters of galaxies with a uniformly selected, spectroscopically complete sample of 35 AGNs in eight clusters of galaxies at z ¼ 0:06 ! 0:31. We find that the 12 AGNs with LX >10 42 ergs s � 1 in cluster members more luminous than a rest-frame MR 10 41 ergs s � 1 do not show evidence for greater central concentration than inactive cluster members, nor evidence for a different kinematic or substructure distribution. As we do see clear differences in the spatial and kinematic distributions of the blue Butcher-Oemler and red cluster galaxy populations, any difference in the AGN and inactive galaxy population must be less distinct than that between these two pairs of populations. Comparison of the AGN fraction selected via X-rayemissioninthisstudytosimilarlyselectedAGNsinthefieldindicatesthattheAGN fractionisnotsignificantly lower in clusters, contrary to AGNs identified via visible wavelength emission lines, but similar to the approximately constant radio-selected AGN fraction in clusters and the field. We also find significant evidence for variation in the AGN fraction between clusters and explore the dependence of cluster AGN fraction on redshift, velocity dispersion, amount of cluster substructure, and fraction of Butcher-Oemler galaxies. While we see weak evidence for several trends, there are several correlations between these four parameters in our small sample of eight clusters that preclude identification of which one(s) most strongly influence the cluster AGN fraction.

Determination of the optical escape factor in the He I line intensity ratio technique applied for weakly ionized plasmas

Radiation trapping of the He I UV resonance transition (λ = 53.7 nm) has been experimentally confirmed in weakly ionized (ionization degree of ∼1–10%)helium plasmas in the PISCES-A linear divertor plasma simulator by using visible line emission with the same upper state as the UV transition. To study the effect of UV opacity on visible line ratios, the radiation trapping of UV resonance transitions was included in a He I collisional–radiative code with the optical escape factor method. The modified code is used to derive electron density ne and temperature Te with the standard He I line intensity ratios, 667.8 nm/728.1 nm and 728.1 nm/706.5 nm. The predicted values of ne and Te are compared with Langmuir probe measurements. Best agreement (within ±30%) is obtained when including radiation trapping and the correct (measured) neutral temperature and using the vacuum chamber radius (as opposed to the smaller plasma radius) for the characteristic length of the system. Neglecting radiation trapping entirely is found to give errors as large as 10 × (3 ×) in the predicted values of ne (Te).

Polarization separated Zeeman spectra from magnetic dipole transitions in highly charged argon in the large helical device

Visible spectral emission lines from magnetic dipole transitions in ArX, ArXI, ArXIV, and ArXV are observed from plasmas heated with neutral-beam injection (NBI) in the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)]. Orthogonal linearly polarized components of the emission line profiles are observed with a polarization separation optical system and high-resolution spectrometer. Zeeman split profiles reveal polarization characteristics of magnetic dipole transitions. Ion temperatures and emission locations are estimated from the profiles with the magnetic field information on the lines of sight (LOS). The spatially resolved emissions are observed by the array of absolutely calibrated views. The time histories of line profiles and emission intensities at the poloidal view are presented. The observed line profiles and the intensity distribution at the poloidal view indicate the localization of these charge states in the edge region just inside the last closed flux surface. The emission line of ArX in the tangential observation indicates Doppler shifts of the Zeeman split profiles. The velocity components of ArX ion flow along the LOS at the tangential view are 7.7 and 2.0km∕s at the outer and inner edge plasmas, respectively, in the opposite direction to the NBI.

Erbium-doped GaN epilayers synthesized by metal-organic chemical vapor deposition

The authors report on the synthesis of Er-doped GaN epilayers by in situ doping by metal-organic chemical vapor deposition (MOCVD). The optical and electrical properties of the Er-doped GaN epilayers were studied by photoluminescence (PL) spectroscopy and van der Pauw–Hall method. Both above and below band gap excitation results in a sharp PL emission peak at 1.54μm. In contrary to other growth methods, MOCVD grown Er-doped GaN epilayers exhibit virtually no visible emission lines. A small thermal quenching effect, with only a 20% decrease in the integrated intensity of the 1.54μm PL emission, occurred between 10 and 300K. It was found that Er incorporation has very little effect on the electrical conductivity of the GaN epilayers and Er-doped layers retain similar electrical properties as those of undoped GaN.

Er 이온 주입된 GaN의 광학적 특성

We have investigated the optical properties of Erbium (Er)-implanted GaN by photoluminescence (PL). Various doses of Er ion were implanted on GaN epilayers by ion implantation. Visible green emission lines due to inner 4f shell transitions for <TEX>$Er^{3+}$</TEX> were observed from the PL spectrum of Er-implanted GaN. The emission spectrum consists of two narrow green lines at 537 and 558 nm. The green emission lines are identified as <TEX>$Er^{3+}$</TEX> transitions from the <TEX>$^{5}H_{11/2}$</TEX> and <TEX>$^{4}S_{3/2}$</TEX> levels to the <TEX>$^{4}I_{15/2}$</TEX> ground state. The stronger peaks in the case with the dose of <TEX>$5{\times}10^{14}cm^{-2}$</TEX>, together with the relatively higher intensity of the <TEX>$Er^{3+}$</TEX> luminescence in the lower doped sample. It implies that some damage remains in the case with the dose of <TEX>$1{\times}10^{16}cm^{-2}$</TEX>. The peak positions of emission lines due to inner 4f shell transitions for <TEX>$Er^{3+}$</TEX> do not change with increasing temperature. It indicates that <TEX>$Er^{3+}$</TEX> related emission depends very little on the ambient temperature.

Interference image spectroscopy for upper atmospheric wind field measurement

Based on the observation of natural airglow and auroral visible emission lines in the upper atmosphere as the explored source, we have surveyed the upper atmosphere wind field through interference imaging spectroscopy coupled with the Doppler effect of electrical and magnetic waves. The velocity and temperature of the upper atmospheric wind field are analyzed and studied. The survey theory and calculation formula of atmosphere wind field in all directions and multi-directions are presented when the relative velocity of the explored source to the detector and their linking line have an arbitrary angle. We also analyzed the effects of the measurement of the upper atmospheric wind field using computer simulation, and explained the reason why the auroral emission line is thought as Gaussian profile.

Energy transfers between Eu2+ and Er3+ in EuGa2S4:Er3+

The photoluminescence properties ofEuGa2S4:Er polycrystals under 337.1 and 976 nm laser excitations versus temperature (78–500 K) arepresented. Under 337.1 nm excitation wavelength, a wide emission band corresponding toEu2+ ions in the visible range and emission lines ofEr3+ in the visible and near infrared were observed. These emissions were also observed under 976 nmexcitation wavelength with a two-photon absorption accompanied by a phonon assisted energy transferto Eu2+ ions. According to experimental conditions, energy transfers fromEu2+ toEr3+ andfrom Er3+ to Eu2+ are highlighted.

Electron micro-probe analysis and cathodoluminescence spectroscopy of rare earth - implanted GaN

ABSTRACTGaN films doped with rare earth (RE) elements have attracted considerable attention due to the unique optical luminescent properties of the RE intra 4ƒ(n)-shell electron transitions which lead to sharp blue (Tm), green (Er) and red (Eu) emissions. This paper presents an overview of investigations of GaN films implanted with each of these ions using a combination of electron-beam and optical techniques. The ion implantations were performed under a wide range of conditions, covering variations in fluences, energies and temperatures and followed by different high-temperature annealing steps. The resulting RE:GaN films were analysed using an electron probe micro-analyser modified to allow cathodoluminescence (CL) spectroscopy. Elemental microanalysis data obtained by wavelength dispersive X-ray analysis (WDX) is correlated with simultaneously collected room temperature CL spectra.WDX allows the quantification of the RE elemental concentrations in GaN down to ∼ 0.03 at. % in very thin layers (∼ 100 nm deep). Furthermore, by varying the incident electron beam energy, details concerning the depth profile of RE implants can be determined. The effects of both implantation conditions and rapid thermal annealing on the depth profile and on the luminescence properties are reported. CL measurements performed on annealed samples reveal sharp visible and near IR emission lines characteristic of the RE3+ intra-4ƒ(n) atomic shell transitions.

Radial Color Gradients in K + A Galaxies in Distant Clusters of Galaxies

Galaxies in rich clusters with z $\gtrsim$ 0.3 are observed to have a higher fraction of photometrically blue galaxies than their nearby counterparts. This raises the important question of what environmental effects can cause the termination of star formation between z $\approx$ 0.3 and the present. The star formation may be truncated due to ram-pressure stripping, or the gas in the disk may be depleted by an episode of star formation caused by some external perturbation. To help resolve this issue, surface photometry was carried out for a total of 70 early-type galaxies in the cluster Cl1358+62, at z $\sim$ 0.33, using two-color images from the Hubble Archive. The galaxies were divided into two categories based on spectroscopic criteria: 24 are type K+A (e.g., strong Balmer lines, with no visible emission lines), while the remaining 46 are in the control sample with normal spectra. Radial color profiles were produced to see if the K+A galaxies show bluer nuclei in relation to their surrounding disks. Specifically, a linear gradient was fit to the radial color profile of each galaxy. We find that the K+A galaxies on average tend to have slightly bluer gradients towards the center than the normals. A Kolmogorov-Smirnov two-sample test has been applied to the two sets of color gradients. The result of the test indicates that there is only a $\sim$2% probability that the K+A and normal samples are drawn from the same parent distribution. There is a possible complication from a trend in the apparent magnitude vs. color gradient relation, but overall our results favor the centralized star formation scenario as an important process in the evolution of galaxies in dense clusters.

Magnetic dipole transitions in titaniumlike ions

Visible and near-UV emission lines of titaniumlike highly charged ions Sb, I, Xe, Ba, Cs, Sm, Eu, Hf, Ta, W, Re, and Pt were observed using an electron beam ion trap. The wavelengths of the magnetic dipole transitions between ground-state fine-structure levels, ${(3d}^{4}{)}^{5}{D}_{J},$ were measured for these elements. These were compared with our own theoretical values, which were obtained with an extended set of configurations, and yielded differences of less than 0.6% for the elements below $Z=60,$ and about 0.1% for those over $Z=60.$

Microscopic Nonthermal Plasma Motions of Coronal Loops in a Solar Active Region

We present a spectroscopic observation of a solar active region NOAA 7590 with a coronagraph at the Norikura Solar Observatory, which provides high-resolution spectra of the visible coronal emission lines (Fe X λ6374, Fe XIV λ5303, Ca XV λ5694) with a spatial sampling of 20×23. Nonthermal velocities (ξ) estimated from Fe X λ6374, Fe XIV λ5303, and Ca XV λ5694 in this observation are 14-20, 10-18, and 16-26 km s-1, respectively. The first two results are consistent with the results obtained by Cheng et al. and others. Even in the Ca XV structures the present observation does not confirm the large nonthermal velocity of 40-60 km s-1 to be typical value. The hypothesis that the nonthermal width in coronal emission lines is due to coronal Alfvén waves is tested by carefully examining the relationship between the width of coronal emission lines and orientation of coronal loops to the line-of-sight direction. From the comparison between edge-on loops in which the direction of magnetic field is nearly parallel to the line-of-sight direction and face-on loops in which the magnetic field is almost perpendicular to the line-of-sight direction, the full width at half-maximum (FWHM) of coronal emission lines for the edge-on loop appears to become smaller near the loop top than that for the face-on loops. The obvious decrease of FWHM of 0.04-0.07 Å (Δξ=3-5 km s-1) is found in the Fe XIV edge-on loops. Although this may be evidence for the Alfvén waves in coronal loops, the velocity amplitude seems to be too small to explain all the nonthermal velocity reported so far.

A tangentially viewing vacuum ultraviolet TV system for the DIII–D divertor

A video camera system capable of imaging vacuum ultraviolet emission in the 120–160 nm wavelength range, from the entire divertor region in the DIII–D tokamak, was designed. The new system has a tangential view of the divertor similar to an existing tangential camera system [M. E. Fenstermacher et al., Rev. Sci. Instrum. 68, 974 (1997)] which has produced two-dimensional maps of visible line emission (400–800 nm) from deuterium and carbon in the divertor region. However, the overwhelming fraction of the power radiated by these elements is emitted by resonance transitions in the ultraviolet, namely the C IV line at 155.0 nm and Ly-α line at 121.6 nm. To image the ultraviolet light with an angular view including the inner wall and outer bias ring in DIII–D, a six-element optical system (f/8.9) was designed using a combination of reflective and refractive optics. This system will provide a spatial resolution of 1.2 cm in the object plane. An intermediate UV image formed in a secondary vacuum is converted to the visible by means of a phosphor plate and detected with a conventional charge injection device (CID) camera (30 ms framing rate). A single MgF2 lens serves as the vacuum interface between the primary and secondary vacuums; a second lens must be inserted in the secondary vacuum to correct the focus at 155 nm. Using the same tomographic inversion method employed for the visible TV, we will reconstruct the poloidal distribution of the UV divertor light. The grain size of the phosphor plate and the optical system aberrations limit the best focus spot size to 60 μm at the CID plane. The optical system is designed to withstand 350 °C vessel bakeout, 2 T magnetic fields, and disruption-induced accelerations of the vessel.