VI Ion Research Articles

Fine structure calculations, polarizability and oscillator strengths for C VI ion embedded in Debye plasma applying accurate Numerov method

The dipole polarizabilities, dipole and quadruple oscillator strengths and relativistic energy corrections are calculated for plasma embedded C VI ion which is of relevance in astrophysics and plasma physics. Numerical simulation of Numerov method is used to find the energy eigenvalues and eigenfunctions by solving the time-independent Schrodinger equation. The dependence of dipole and quadruple polarizabilities, oscillator strengths and relativistic energy corrections on Debye length is shown.

Fast and Efficient Removal of Dyes and Cr(Vi) Ion from Wastewater Using Halloysite Nanotubes-Covalently Coated Polyurethane Sponges

Fast and Efficient Removal of Dyes and Cr(Vi) Ion from Wastewater Using Halloysite Nanotubes-Covalently Coated Polyurethane Sponges

Photothermal and magnetocaloric-stimulated shape memory and self-healing via magnetic polymeric composite with dynamic crosslinking

Multiple-stimulated shape-memory and self-healing materials can be employed in some covert circumstances and special system because of the flexible control manners, which shows great potential in practical application. In this work, Fe3O4 grafted copolymer, Fe3O4-g-P(TMA-co-LA-co-VI), with magnetic, near-infrared light and thermo multiple-stimulated shape memory and self-healing performance, was synthesized, where tetrahydrofurfuryl methacrylate (TMA), lauryl acrylate (LA) and 1-vinylimidazole (VI) were biomass derived monomers. Dynamic metal-ligand network in Fe3O4-g-P(TMA-co-LA-co-VI)/Zn was subsequently constructed via the coordination of VI and zinc ion. The mechanical properties of the nanocomposite could be simply regulated by varying the Fe3O4 content and the molar ratio of monomers. Among all the samples, Fe3O4-g-P(TMA-co-LA-co-VI)/Zn with Fe3O4 content of 1 wt % and TMA/LA/VI molar ratio of 8/2/2.5 showed a breaking stain of 300% and a maximum stress of 1.66 MPa, which also showed an excellent thermo stimulated shape memory and self-healing performance. As the Fe3O4 nanoparticles were uniformly dispersed in the nanocomposites, their photothermal and magnetocaloric transformation can efficiently stimulate the dynamic and reversible metal-ligand crosslinked process between VI and Zn2+. Therefore, this kind of effective stimulation can finally lead to excellent remote-controllable shape memory and self-healing performance. The integration of magnetic, near-infrared light and thermo multiple-stimulation for shape memory and self-healing also augurs well for their wide application potential in artificial intelligence materials and life science.

Adsorption of Cr(Vi) Ion from Aqueous Solutions by Solid Waste of Potato Peels

Pollution of wastewater with heavy metal has always been a serious problem to the environment. Chromium is considered one of the most noxious heavy metals. Adsorption is now reorganized as an alternative technology of defence for chromium removal due to local availability, technical efficiency and cost effectiveness. Potato peel powder can be used as a low cost biosorbent to remove hexavalent chromium from aqueous solutions under various experimental conditions. Different parameters including equilibrium contact time, initial metal ion concentration, potato peel dose, pH and temperature were studied through a number of batch sorption experiments. Both the Langmuir and Freundlich were found to fit the adsorption isotherm of Cr (VI) ion onto potato peel. The Langmuir adsorption capacity was found to be 1.97 mg/g while Freundlich constants including Kf and n were 1.57 and 2.5, respectively. The adsorption kinetic was found to be more fit with the pseudo-first order model. This study showed a high efficiency of potato peel for the biosorption of Cr (VI) ion from aqueous solutions.

Electron density diagnostics by use of a collisional excitation model of the oxygen VI doublet in the solar transition region

ABSTRACTFor spectral diagnostics in the solar transition region under the collision–equilibrium condition, the method for electron density diagnostics by the collisional excitation is discussed in this paper. By using observed signal ratio of spectral lines produced by the oxygen VI ion, we discuss the electron density by this method. We find that this method is valid for a large region of signal ratio (from 2.001 to 4.162). We obtain that the electron density increases with increasing signal ratio of the oxygen VI doublet, and the plasma has an electron density on the order of magnitude of 106–107 cm−3. This discussion will be significant for study on spectral diagnostics of the solar transition region.

Ion–Cyclotron Resonance Frequency Interval Dependence on the O VI Ion Number Density in the North Polar Coronal Hole 1.5R–3R Region

The frequency intervals in which O VI ions get in resonance with ion–cyclotron waves are calculated using the kinetic model, for the latest six values found in literature on O VI ion number densities in the 1.5R–3R region of the NPCH. It is found that the common resonance interval is 1.5 kHz to 3 kHz. The R-variations of wave numbers necessary for the above calculations are evaluated numerically, solving the cubic dispersion relation with the dielectric response derived from the quasi-linear Vlasov equation for the left-circularly polarized ion-cyclotron waves.

Electron impact excitation for Ar VI

Radiative atomic and electron impact excitation data for Ar VI ion have been calculated using the AUTOSTRUCTURE code. The two-body non-fine structure operators of the Breit-Pauli Hamiltonian have been incorporated in AUTOSTRUCTURE, and for the collisional problem, we use the distorted wave approximation. We compare our radiative atomic results with the few available ones. To our best knowledge, there are no distorted wave collision strengths for Ar VI. Some discrepancies have been reported between our oscillator strengths and the only calculated ones using the MCHF method. We perform the same calculations with the UCL codes SST/DW/JAJOM and we compare with the present AUTOSTRUCTURE results.

THE DIAGNOSTIC O VI ABSORPTION LINE IN DIFFUSE PLASMAS: COMPARISON OF NON-EQUILIBRIUM IONIZATION STRUCTURE SIMULATIONS TO FUSE DATA

The nature of the interstellar O VI in the Galactic disk is studied by means of a multi-fluid hydrodynamical approximation, tracing the detailed time-dependent evolution of the ionization structure of the plasma. Our focus is to explore the signature of any non-equilibrium ionization condition present in the interstellar medium using the diagnostic O VI ion. A detailed comparison between the simulations and FUSE data is carried out by taking lines of sight (LOS) measurements through the simulated Galactic disk, covering an extent of 4 kpc from different vantage points. The simulation results bear a striking resemblance with the observations: (1) the N(O VI) distribution with distance and angle fall within the minimum and maximum values of the FUSE data; (2) the column density dispersion with distance is constant for all the LOS, showing a mild decrease at large distances; (3) O VI has a clumpy distribution along the LOS; and (4) the time-averaged midplane density for distances >400 pc has a value of (1.3-1.4) Multiplication-Sign 10{sup -8} cm{sup -3}. The highest concentration of O VI by mass occurs in the thermally stable (10{sup 3.9} K < T {<=} 10{sup 4.2} K; 20%) and unstable (10{sup 4.2} K < T <more » 10{sup 5} K; 50%) regimes, both well below its peak temperature in collisional ionization equilibrium, with the corresponding volume filling factors oscillating with time between 8%-20% and 4%-5%, respectively. These results may also be relevant for intergalactic metal absorption systems at high redshifts.« less

Development of two-grating spectrometer for the charge exchange spectroscopy system on KSTAR

The charge exchange spectroscopy (CES) system on Korea Superconducting Tokamak Advanced Research (KSTAR) was installed last year and had been applied to measure the C VI ion temperature and rotation velocity profiles. The ion temperature and rotation velocity profiles had been estimated from the C VI 5290.5 Å (n = 8-7) charge-exchange spectrum signal measured by a Czerny-Turner type spectrometer and a thinned back-illuminated charge coupled device (CCD) camera. However, the Czerny-Turner type spectrometer used for the KSTAR CES system showed so low signal to noise ratio for KSTAR plasmas in the 2010 experimental campaign that the time resolution of the CES system had been limited to 100 ms due to the increased exposure time of the attached CCD camera. Then, new two-grating spectrometer had been developed in order to improve the time resolution of the CES system. The spectrometer consists of two gratings (1200 g/mm and 1800 g/mm each) with additive configuration, concave mirrors (f = 50 cm), and a cylindrical lens (f = 50 cm). The time resolution of the CES system increases by a factor of 2-4 with the two-grating spectrometer. The C VI ion temperature and rotation velocity profiles obtained by the two-grating spectrometer are compared to those by Czerny-Turner type spectrometer in this paper.

THE ELECTRON TEMPERATURE OF THE SOLAR TRANSITION REGION AS DERIVED FROM EIS AND SUMER

We use UV and extreme-UV emission lines observed in quiet regions on the solar disk with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument and the Extreme Ultraviolet Imaging Spectrometer (EIS) to determine the electron temperature in solar transition region plasmas. Prominent emission lines of O IV and O VI are present in the solar spectrum, and the measured intensity line ratios provide electron temperatures in the range of log T = 5.6-6.1. We find that the theoretical O IV and O VI ion formation temperatures are considerably lower than our derived temperatures. The line ratios expected from a plasma in ionization equilibrium are larger by a factor of about 2-5 than the measured line ratios. A careful cross-calibration of SUMER and EIS has been carried out, which excludes errors in the relative calibration of the two instruments. We checked for other instrumental and observational effects, as well as line blending, and can exclude them as a possible source of the discrepancy between theoretical and observed line ratios. Using a multi-thermal quiet-Sun differential emission measure changes the theoretical line ratio by up to 28% which is not sufficient as an explanation. We also explored additional excitation mechanisms. Photoexcitation from photospheric blackbody radiation, self-absorption, and recombination into excited levels cannot be a possible solution. Adding a second Maxwellian to simulate the presence of non-thermal, high-energy electrons in the plasma distribution of velocities also did not solve the discrepancy.

The nature and origin of low-redshift O vi absorbers

The O VI ion observed in quasar absorption-line spectra is the most accessible tracer of the cosmic metal distribution in the low-redshift ( z< 0.5) intergalactic medium (IGM). We explore the nature and origin of O VI absorbers using cosmological hydrodynamic simulations including galactic outflows with a range of strengths. We consider the effects of ionization background variations, non-equilibrium ionization and cooling, uniform metallicity and small-scale (subresolution) turbulence. Our main results are as follows. (1) IGM O VI is predominantly photoionized with T ≈ 10 4.2±0.2 K. A key reason for this is that O VI absorbers preferentially trace overenriched (by ∼× 5) regions of the IGM at a given density, which enhances metal-line cooling such that absorbers can cool to photo-ionized temperatures within a Hubble time. As such, O VI is not a good tracer of the warm-hot intergalactic medium. (2) The predicted O VI properties fit observables if and only if sub-resolution turbulence is added, regardless of any other model variations. The required turbulence increases with O VI absorber strength. Stronger absorbers arise from more recent outflows, so qualitatively this can be understood if IGM turbulence dissipates on the order of a Hubble time. The amount of turbulence is consistent with other examples of turbulence observed in the IGM and galactic haloes. (3) Metals traced by O VI and H I do not trace exactly the same baryons, but reside in the same large-scale structure. Our simulations reproduce observed alignment statistics between O VI and H I, yet aligned absorbers typically have O VI arising from cooler gas, and for stronger absorbers lower densities, than H I. Owing to peculiar velocities dominating the line structure, coincident absorption often arises from spatially distinct gas. (4) Photo-ionized O VI traces gas in a variety of environments, and is not directly associated with the nearest galaxy, though is typically nearest to ∼0.1L∗ galaxies. Weaker O VI components trace some of the oldest cosmic metals. (5) Very strong absorbers (EW 100 mA) are more likely to be collisionally ionized, tracing more recent enrichment (2 Gyr) within or near galactic haloes.

The Influence of Stellar Wind Variability on Measurements of Interstellar O [CSC]vi[/CSC] along Sight Lines to Early-Type Stars

A primary goal of the Far Ultraviolet Spectroscopic Explorer mission is to understand the origin of the O VI ion in the interstellar medium of the Galaxy and the Magellanic Clouds. Along sight lines to OB-type stars, these interstellar components are usually blended with O VI stellar wind profiles, which frequently vary in shape. In order to assess the effects of this time-dependent blending on measurements of the interstellar O VI lines, we have undertaken a minisurvey of repeated observations toward OB-type stars in the Galaxy and the Large Magellanic Cloud. These sparse time series, which consist of two to three observations separated by intervals ranging from a few days to several months, show that wind variability occurs commonly in O VI (~60% of a sample of 50 stars), as indeed it does in other resonance lines. However, in the interstellar O VI ?1032 region, the O VI ?1038 wind varies only in ~30% of the cases. By examining cases exhibiting large amplitude variations, we conclude that stellar wind variability generally introduces negligible uncertainty for single interstellar O VI components along Galactic lines of sight but can result in substantial errors in measurements of broader components or blends of components like those typically observed toward stars in the Large Magellanic Cloud. Due to possible contamination by discrete absorption components in the stellar O VI line, stars with terminal velocities greater than or equal to the doublet separation (1654 km s-1) should be treated with care.

High time resolution ion temperature and rotation velocity measurements by charge exchange spectroscopy using three interference filters

The ion temperature and toroidal rotation velocity with high time resolution (τ∼1 ms) using charge exchange spectroscopy in JT-60U tokamak plasma have been measured. The method uses three interference filters that have slightly different peak wavelengths. These filters are selected according to the ion temperature and rotation velocity expected at the measured position. The system with a time resolution of 1 ms was applied to the analysis of fast plasma phenomena. As an example, the time evolution of the C VI ion temperature and toroidal rotation velocity across the L–H transition has been measured. The toroidal rotation at a normalized minor radius (r/a=0.3) increases gradually after the L–H transition, while that at the edge changes from a speed of 5 km/s before the transition to −40 km/s after the transition within a time of 5–10 ms.

Computational simulation of a recombination x-ray C VI ion laser pumped with 2 ps pulses

Calculations are made of lasing resulting from the 3 — 2 transition in the C ion VI under the same conditions as in an experimental investigation of the VULCAN recombination x-ray laser at the Rutherford Appleton laboratory. A carbon filament target with a diameter of 7 μm and up to 5 mm long was irradiated with Nd laser pulses (λ =1.053 μm) of ∼ 2.4 ps duration and ∼ 20 J energy. The calculated space-and-time average value of the gain coefficient at the 18.2 nm wavelength was ∼18 cm-1 for the specific absorbed energy. This was in satisfactory agreement with the experimental results. The optimal lasing conditions for the investigated target irradiation conditions were estimated.

More confirmed damped Lyman-Alpha systems from the Las Campanas/Palomar survey

view Abstract Citations (27) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS More Confirmed Damped Lyman-Alpha Systems From the Las Campanas/Palomar Survey Lu, Limin ; Wolfe, Arthur M. Abstract We present moderate-resolution spectra of six high-redshift quasars which contain nine candidate damped Lyα absorption systems identified in the Las Campanas/Palomar survey of Lanzetta et al. [ApJS, 77, 1 (1991)]. Eight of the nine candidate damped Lyα absorption systems are confirmed (one tentative), including seven with N(H I) >= 2 x 10^20^ cm^- 2^. The remaining one turns out to be due to blending of many narrow absorption lines. Accurate absorption redshifts, HI column densities, and metal-line equivalent widths are provided for these systems in order to facilitate future studies of detailed physical condition and chemical abundances. We briefly discuss the 18 other metal-line systems identified along these sight lines. The z_abs_ = 2.6527 system toward Q 2231-00 is interesting in that it shows strong O VIλλ1031, 1037 absorption. The O VI ion is one of the best diagnostics of hot gas, and high resolution studies of the O VI absorption is likely to yield important clues regarding the ionization mechanism of the metal-line systems. Another system, at z_abs_ = 2.377l toward Q 2239-38, shows relatively strong Zn II and Cr II absorption, clearly indicating that it belongs to the same class absorbers as the damped Lyα systems. We have not obtained metal abundances for this system because the H I column density is not available. We also find a Lyman limit absorption system at z_abs_ = 3.5090 toward Q 2239-38 which does not show obvious metal absorption lines. More sensitive observations are required to check on this interesting possibility. Publication: The Astronomical Journal Pub Date: July 1994 DOI: 10.1086/117043 Bibcode: 1994AJ....108...44L Keywords: Astronomical Catalogs; Lyman Alpha Radiation; Lyman Spectra; Quasars; Red Shift; Galactic Evolution; Radio Astronomy; Astrophysics; QUASARS: ABSORPTION LINES; STARS: ABUNDANCES full text sources ADS | data products NED (25) SIMBAD (6)

Numerical simulation of a recombination x-ray laser

A numerical model of a recombination x-ray laser has been developed. A calculation on the gasdynamics of a plasma with nonequilibrium diffusion of thermal radiation includesthe stage of laser irradiation of the target. A model for the kinetics of the level populations of hydrogen-like ions incorporates reabsorption of Lyman lines through an exact solution of the transport equation in a cylindrical inhomogeneous plasma.The dynamic Doppler effect is taken into account. Experiments carried out at the Rutherford Appleton Laboratory to observe a gain on the 3-2 transition of the C VI ion in the expanding plasma of a carbon fiber are analyzed numerically. A satisfactory description of the experimental results is found when account is taken of the fine splitting of the working levels and of the distortion of the signal by the measurement apparatus.

Detailed modelling of the hydrogenic carbon expansion cooled recombination laser

The agreement between experimental results and theoretical predictions is improved for the temporal dynamics of the gain coefficient on the 3 to 2 transition of the C VI ion at 182 AA. It is shown that nj kinetics improves the description of radiative cleaning of the n=2 level in a partially reabsorbed, expanding plasma, surprisingly increasing the degree of frozen ionization. A detailed description of radiative trapping on the n=2,3 levels is included in the model in the form of the net radiative bracket, calculated through an exact solution of the radiative transfer problem. The accurate treatment of radiative transport is found to convincingly verify the Sobolev formulation of the escape factor.

Calculation of the gain of a C VI laser plasma expanding as a cylinder and a cylindrical layer

Calculations are reported of the gain due to the 3–2 transition in the C VI ion in an expanding plasma cylinder or a cylindrical layer. Under the conditions in the experiments at the Rutherford Appleton Laboratory (Chilton, England) amplification was observed as a result of evaporation of a fairly thin (~ 0.1 μm) cylindrical layer. A peak of the gain was reached in a relatively short time (~ 0.1 ns).

Density Diagnostics of Solar Emission Lines from the Nitrogen-like Mg VI Ion

The variation of theoretical line intensity ratios with electron density for Mg VI ion are presented. This study indicates that the line intensity ratios for Mg VI can be used to infer electron density for solar plasma.

Amplification of radiation in a transversely inhomogeneous plasma filament

An analysis is made of the amplification of radiation in long plasma filaments. The analysis is made using spatially two-dimensional models of the emission dynamics. The general conclusions are illustrated by calculations of the gain due to the 3–2 transition in the C VI ion. It is shown that on the basis of recombination pumping of carbon filaments of ~ 1 μm initial radius, it is possible to develop a far ultraviolet laser exhibiting modest energy parameters and being of some interest for fundamental scientific research.