Emission Line Intensity Ratios Research Articles

Electron density dependence of intensity ratio for FeXXII extreme ultraviolet emission lines arising from different ground levels in electron beam ion trap and large helical device

Extreme ultraviolet (EUV) spectra of highly charged iron ions in a wavelength range of 100–300 Å have been observed from two different plasma sources of the Tokyo Electron Beam Ion Trap (Tokyo-EBIT) with a monoenergetic electron beam and a Large Helical Device (LHD) with Maxwellian electron energy. The excitation process of the spectral lines is compared between the two plasmas, and it is found that the excitation process for Fe XIX - Fe XXII ions is clearly different. Namely, the EUV emission lines from the EBIT plasma are only dominated by electron impact excitation connected to the ground state, but the excitation mechanism is not so simple in the LHD plasma. The difference in the excitation process is studied by measuring the intensity ratio of EUV emission lines (114.412 Å [1s22s2p2 2P3/2 → 1s22s22p 2P3/2]/117.144 Å [1s22s2p2 2P1/2 → 1s22s22p 2P1/2]) arising from different ground levels in the Fe XXII ions. The line intensity ratio has an extremely small value of 0.2 in the EBIT plasma with a low beam current of 30 mA and a beam energy of 2 keV, while the ratio varies with the electron density ne in the LHD plasmas, i.e., 0.35 for ne = 1 × 1013 cm−3 and 0.65 for ne = 4 × 1013 cm−3. Here, the electron density of the EBIT plasma is estimated to be smaller than 1012 cm−3 and the electron temperature of the LHD plasmas is 2 keV. The dependence of the line intensity ratio on the observed electron density is analyzed for both the EBIT and the LHD plasmas using several collisional-radiative (CR) models. The present experimental data can easily be reproduced by the analysis when the thermal proton impact excitation is taken into account. The importance of the proton impact excitation is also experimentally verified by injecting an iron pellet into the LHD plasmas and changing the ratio of the proton density to the electron density.

Spectropolarimetry of the Superwind Filaments of the Starburst Galaxy M 82: Kinematics of Dust Outflow

Spectropolarimetry results for the starburst galaxy M 82 are presented. The optical emission lines of the filaments in the energetic outflow (``superwind'') from the nuclear starburst region of M 82 are substantially polarized. The H$\alpha$ polarization degrees and angles measured by our study are consistent with previous narrowband imaging polarimetry data. The polarized emission lines are redshifted with respect to the emission lines in the total light and systemic motion of the galaxy. The emission line intensity ratios [N II]$/$H$\alpha$ and [S II]$/$H$\alpha$ in the polarized light are similar to those of the nuclear star-forming region. In addition, the electron density $N_{\rm e}$ derived from the [S II]$\lambda$6731$/\lambda$6717 line ratio of the polarized light is $\sim\ $600–1000 cm$^{-3}$ at a distance of more than 1 kpc from the nucleus, whereas the $N_{\rm e}$ derived from the total light are less than 300 cm$^{-3}$. These facts strongly suggest that the emission from the nuclear starburst of M 82 is scattered by dust grains entrained and transported outward by the superwind. A simple hollow biconical outflow model shows that the velocity of the outflowing dust grains, $v_{\rm d}$, ranges from 100 to 200 km s$^{-1}$ near the nucleus, decreases monotonically with the distance from the nucleus, and reaches $\sim\ $10 km s$^{-1}$ at around 1 kpc. The motion of the dust is substantially slower than that of both ionized gas ($v_{{\rm H}\alpha}$$\sim\ $ 600 km s$^{-1}$) and molecular gas ($v_{\rm CO}$$\sim\ $ 200 km s$^{-1}$) at the same distance from the nucleus of M 82. This indicates that dust grains in the superwind are kinematically decoupled from both gas components at large radii. Since the dust velocity $v_{\rm d}$ is much less than the escape velocity of M 82 ($v_{\rm esc}$$\approx$ 170 km s$^{-1}$ at 1.5 kpc from the nucleus), most of the dust entrained by the superwind cannot escape to intergalactic space, and may fall back into the galaxy disk if there is no additional acceleration mechanism (such as radiation pressure).

Hinode extreme-ultraviolet imaging spectrometer observations of a limb active region

Aims. We investigate the electron density and temperature structure of a limb active region. Methods. We have carried out a study of an active region close to the solar limb using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-ray telescope (XRT) on board Hinode. The electron density and temperature distributions of the coronal emission have been determined using emission line intensity ratios. Differential emission measure (DEM) analysis and the emission measure (EM) loci technique were used to examine the thermal structure of the emitting plasma as a function of distance from the limb. Results. The highest temperature and electron density values are found to be located in the core of the active region, with a peak electron number density value of 1.9 × 10 10 cm −3 measured using the Fe XII 186.887 A to 192.394 A line intensity ratio. The plasma along the line of sight in the active region was found to be multi-thermal at different distances from the limb. The EIS and XRT DEM analyses appear to be in agreement in the temperature interval from log T = 6.5−6.7. Conclusions. Our results provide new constraints for models of coronal heating in active regions.

Luminescence properties of Tb doped and Tm/Tb/Sm co-doped glasses for LED applications

Tb 3+ ions doped and Tm/Tb/Sm co-doped glasses for light-emitting-diodes (LED) applications have been synthesized by melt quenching method. Their photoluminescence properties were studied by emission and excitation spectra. The 5D 3 and 5D 4 emission of Tb 3+ can be varied by adjusting Tb 3+ concentrations and the compositions of glass matrix. Blue, green and reddish orange emission bands were observed in the emission spectra of Tm/Tb/Sm co-doped glasses. The combination of these emission bands allows the realization of white light when the glasses are excited by near ultraviolet light. In addition, the relative intensity ratios of respective emission lines are dependent on the composition of glasses and the excitation wavelength.

Influence of additional magnetic field on plasma parameters in magnetron sputtering

With three additional magnetic rings being assembled outside the discharge room and connected with the magnetic field of the conventional unbalanced magnetron sputtering, a closed magnetic field configuration distribution had been formed in the whole discharge room and which can confine discharge plasma more effectively. The spatial distribution of the newly designed magnetic field configuration was simulated using the ANSYS software. Plasma potential, electron temperature, electron density and ion density in the discharge plasma were diagnosed by Langmuir probe and the optical emission line intensity ratios of Ar +/Ar and Cu +/Cu were studied by optical emission spectroscopy. The structure and morphology of the Cu films are measured by scanning electron microscopy. A comparative study of the new magnetic field configuration with the conventional unbalanced magnetic field configuration was conducted. The results showed that the application of the additional magnetic field can increase the plasma density, enhance the ionization degree of the sputtered Cu and decrease the plasma potential effectively. The characteristics of the deposited Cu film were also influenced by the new magnetic field configuration greatly.

Feeding versus feedback in NGC 4151 probed with Gemini NIFS - I. Excitation

We have used the Gemini Near-infrared Integral Field Spectrograph (NIFS) to map the emission-line intensity distributions and ratios in the narrow-line region (NLR) of the Seyfert galaxy NGC 4151 in the Z, J, H and K bands at a resolving power ≥5000, covering the inner ≈200 × 300 pc of the galaxy at a spatial resolution of ≈8 pc. We present intensity distributions in 14 emission lines, which show three distinct behaviours. (1) Most of the ionized gas intensity distributions are extended to ≈100 pc from the nucleus along the region covered by the known biconical outflow (position angle, PA = 60/240°, NE–SW), consistent with an origin in the outflow; while the recombination lines show intensity profiles which decrease with distance r from the nucleus as I∝r−1, most of the forbidden lines present a flat intensity profile (I∝r0) or even increasing with distance from the nucleus towards the border of the NLR. (2) The H2 emission lines show completely distinct intensity distributions, which avoid the region of the bicone, extending from ≈10 to ≈60 pc from the nucleus approximately along the large-scale bar, almost perpendicular to the bicone axis. This morphology supports an origin for the H2-emitting gas in the galaxy plane. (3) The coronal lines show a steep intensity profile, described by I∝r−2; the emission is clearly resolved only in the case of [Si vii], consistent with an origin in the inner NLR. Using the line-ratio maps [Fe ii] 1.644/1.257 and Pa β/Br γ, we obtain an average reddening of E(B−V) ≈ 0.5 along the NLR and E(B−V) ≥ 1 at the nucleus. Our line-ratio map [Fe ii] 1.257 μm/[P ii] 1.189 μm of the NLR of NGC 4151 is the first such map of an extragalactic source. Together with the [Fe ii]/Paβ map, these line ratios correlate with the radio intensity distribution, mapping the effects of shocks produced by the radio jet on the NLR. These shocks probably release the Fe locked in grains and produce an enhancement of the [Fe ii] emission at ≈1 arcsec from the nucleus. At these regions, we obtain electron densities Ne≈ 4000 cm−3 and temperatures Te≈ 15 000 K for the [Fe ii]-emitting gas. For the H2-emitting gas, we obtain much lower temperatures of Texc≈ 2100 K and conclude that the gas is in thermal equilibrium. The heating necessary to excite the molecule may be due to X-rays escaping perpendicular to the cone (through the nuclear torus, if there is one) or to shocks probably produced by the accretion flow previously observed along the large-scale bar. The distinct intensity distributions and physical properties of the ionized and molecular gas, as well as their locations, the former along the outflowing cone, and the latter in the galaxy plane surrounding the nucleus, suggest that the H2-emitting gas traces the active galactic nuclei feeding, while the ionized gas traces its feedback.

Line intensity enhancements in stellar coronal X-ray spectra due to opacity effects

Context. The I(15.01 A)/I(16.78 A) emission line intensity ratio in Fe xvii has been reported to deviate from its theoretical value in solar and stellar X-ray spectra. This is attributed to opacity in the 15.01 A line, leading to a reduction in its intensity, and was interpreted in terms of a geometry in which the emitters and absorbers are spatially distinct. Aims. We study the I(15.01 A)/I(16.78 A) intensity ratio for the active cool dwarf EV Lac, in both flare and quiescent spectra. Methods. The observations were obtained with the Reflection Grating Spectrometer on the XMM-Newton satellite. The emission measure distribution versus temperature reconstruction technique is used for our analysis. Results. We find that the 15.01 A line exhibits a significant enhancement in intensity over the optically thin value. To our knowledge, this is the first time that such an enhancement has been detected on such a sound statistical basis. We interpret this enhancement in terms of a geometry in which the emitters and absorbers are not spatially distinct, and where the geometry is such that resonant pumping of the upper level has a greater effect on the observed line intensity than resonant absorption in the line-of-sight.

Hydrocarbon plasma chemistry in a continuous microwave discharge

A study is made of the relation between the kinetic processes involving carbon-containing species and the intensity ratios of different emission lines in synthesizing diamond films in a microwave discharge plasma. The intensity ratios of the emission lines are measured as functions of the pressure, composition, and flow rate of the gas mixture. The kinetic processes involving carbon-containing components are simulated under conditions close to the experimental ones. It is shown that the intensity ratios of different pairs of lines can be used to control diamond film deposition.

Local electronic structure of Mn dopants in ZnO probed by resonant inelastic x-rayscattering

The electronic structure of Mn dopants in ZnO epitaxial thin films synthesized at differenttemperatures has been investigated using resonant inelastic x-ray scattering. The resulting MnL2,3 x-ray emissionspectra of Zn0.8Mn0.2O (resonantly excited at L2 and L3 absorption edges) reveal different spectral features depending on thegrowth temperature of the films. The relative integral intensity ratio of MnL2 toMn L3 emission lines is greatly suppressed in the case of nonmagneticZn0.8Mn0.2O grownat 700 °C due to L2L3M4,5 Coster–Kronig transitions. The ferromagnetic sample grown at600 °C exhibits a normal oxide structure. The results suggest that a high growth temperaturecauses direct Mn–Mn bonds from the segregation of Mn atoms in ZnO. Therefore thedisappearance of ferromagnetism in Mn-doped ZnO can be attributed to antiferromagneticMn–Mn exchange interactions due to the inhomogeneous local environment around the Mnimpurities.

SPEARfar UV spectral imaging of highly ionized emission from the North Galactic Pole region

Aims. We present far ultraviolet (FUV: 912–1750 A) spectral imaging observations recorded with the SPEAR satellite of the interstellar OVI (1032 A), CIV (1550 A), SiIV (1394 A), SiII* (1533 A) and AlII (1671 A) emission lines originating in a 60 ◦ × 30 ◦ rectangular region lying close to the North Galactic Pole. These data represent the first large area, moderate spatial resolution maps of the distribution of UV spectral-line emission originating the both the highly ionized medium (HIM) and the warm ionized medium (WIM) recorded at high galactic latitudes. Methods. By assessing and removing a local continuum level that underlies these emission line spectra, we have obtained interstellar emission intensity maps for the aforementioned lines constructed in 8 ◦ × 8 ◦ spatial bins on the sky. Results. Our maps of OVI, CIV, SiIV and SiII* line emission show the highest intensity levels being spatially coincident with similarly high levels of soft X-ray emission originating in the edge of the Northern Polar Spur feature. However, the distribution of the low ionization AlII emission does not show this spatial correlation, and suggests that warm-neutral and/or partially ionized gas with a temperature <20 000 K may be quite pervasive at high galactic latitudes. The variation of the emission line intensity ratios as a function of sky position is contrasted with theoretical predictions concerning the physical state of interstellar gas in the galactic halo. The observed line ratios alone unfortunately do not provide us with a clear diagnostic tool to distinguish between the various physical production mechanisms responsible for both high and low ion states. However, our results do favor the hybrid model of Shull & Slavin (1994, ApJ, 427, 784) which incorporates the combined effects of turbulent mixing layers and isobarically cooling supernova remnant gas. For this highly ionized gas, our results are best explained assuming that the observed OVI halo emission is somewhat clumpy in nature, consistent with its production at interfaces between warm (T = 10 3 −10 4 K) and hotter (T = 10 6 K) soft X-ray emitting gas. CIV emission at these interfaces occurs in the intermediate temperature (T = 10 5 K) gas, which seems always present whenever OVI is strongly detected. Alternately, the data are also consistent with CIV emission being ubiquitous throughout the halo with a fairly constant level of emission line intensity (of ∼4000 LU), and our observations mostly reflect the superposition of spatially separate OVI emission originating at the cloud interfaces of random clumps of high latitude gas.

Post-annealing effect on the electronic structure of Mn atoms inGa1−xMnxAs probed by resonant inelastic x-ray scattering

The electronic structure of as-grown and post-annealedGa1−xMnxAs epilayers (x≈0.055) has been investigated using resonant inelastic x-ray scattering. MnL2,3 x-ray emission spectra show that the integral intensity ratio of MnL2 toL3 emission lines increases with annealing temperature and comes close to that ofmanganese oxide. The oxygen K-emission/absorption spectra of post-annealedGa0.945Mn0.055As show 1.5–3.0 times higher degree of oxidation on the film surface than that of the as-grownsample. These experimental findings are attributed to the diffusion of Mn impurity atomsfrom interstitial positions in the GaAs host lattice to the surface where they are passivatedby oxygen.

Searching for X-ray luminous “normal” galaxies in 2dFGRS

We cross-correlated the Chandra XASSIST and XMM-Newton Serendipitous Source Catalogues with the 2 degree Field Galaxy Redshift Survey (2dfGRS) database. Our aim was to identify the most X-ray luminous (L_X > 10^42 erg s^-1) examples of galaxies in the local Universe whose X-ray emission is dominated by stellar processes rather than AGN activity ('normal' galaxies) as well as to test the empirical criterion log(f_X/f_O) < -2 for separating AGN from NGs. With XMM-Newton (Chandra) we covered an area of ~8.2 (~5.8)deg^2 down to a flux limit of ~10^-15 (~1.6 x 10^-15) erg cm^-2 s^-1 and found 18 (20) 2dfGRS galaxies. Using emission-line intensity ratios, we classified 6 2dfGRS spectra as star-forming, H II nuclei, and 2 spectra as possible H II nuclei. The rest of the objects are absorption-line galaxies and AGN, including 3 possible LINERs. No luminous 'normal' galaxies have been found but out of 19 'normal' galaxies in this sample 5 H II and 3 absorption-line galaxies have log(f_X/f_O) > -2. We performed a similar search in two nearby-galaxy samples from the literature. All 44 galaxies in the Zezas (2001) sample have log(f_X/f_O) < -2 and L_X < 10^42 erg s^-1. In the Fabbiano et al. (1992) sample, out of a total of 170 'normal' galaxies, we found 16 galaxies with log(f_X/f_O) >-2, the majority of which are massive ellipticals. Three of these have L_X > 10^42 erg s^-1 .

Radio Measurements of the Height of Strong Coronal Magnetic Fields Above Sunspots at the Solar Limb

We measure coronal magnetic field strengths of 1750 G at a height of 8000 km above a large sunspot in NOAA AR 10652 at the west solar limb on 2004 July 29 using coordinated observations with the Very Large Array, the Transition Region and Coronal Explorer, and three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric Observatory. This observation is the first time that coronal radio brightness temperatures have been analyzed in a 15 GHz solar radio source projected above the limb. Observations at 8 GHz yield coronal magnetic field strengths of 960 G at a height of 12,000 km. The field strength measurements combine to yield a magnetic scale height LB = 6900 km. The radio brightness temperature maxima are located away from a sunspot plume that appears bright in EUV line emission formed at temperatures around several ×105 K. We use the density-sensitive emission-line intensity ratio of O IV 625.8 A/554.5 A to derive an electron density ne (in units of cm-3) of log ne = 10.1 ± 0.2 at the base of the plume.

Multivariate Characterization of Hydrogen Balmer Emission in Cataclysmic Variables

AbstractThe ratios of hydrogen Balmer emission line intensities in cataclysmic variables are signatures of the physical processes that produce them. To quantify those signatures relative to classifications of cataclysmic variable types, we applied the multivariate statistical analysis methods of principal components analysis and discriminant function analysis to the spectroscopic emission data set of Williams (1983). The two analysis methods reveal two different sources of variation in the ratios of the emission lines. The source of variation seen in the principal components analysis was shown to be correlated with the binary orbital period. The source of variation seen in the discriminant function analysis was shown to be correlated with the equivalent width of the Hβ line. Comparison of the data scatterplot with scatterplots of theoretical models shows that Balmer line emission from T CrB systems is consistent with the photoionization of a surrounding nebula. Otherwise, models that we considered do not reproduce the wide range of Balmer decrements, including ‘inverted’ decrements, seen in the data.

FexiEmission Lines in a High‐Resolution Extreme‐Ultraviolet Active Region Spectrum Obtained by the Solar Extreme Ultraviolet Research Telescope and Spectrograph

New calculations of radiative rates and electron impact excitation cross sections for Fe XI are used to derive emission-line intensity ratios involving 3s23p4-3s23p33d transitions in the 180-223 Å wavelength range. These ratios are subsequently compared with observations of a solar active region obtained during the 1995 flight of the Solar Extreme Ultraviolet Research Telescope and Spectrograph (SERTS). The version of SERTS flown in 1995 incorporated a multilayer grating that enhanced the instrumental sensitivity for features in the ~170-225 Å wavelength range, observed in second order between 340 and 450 Å. This enhancement led to the detection of many emission lines not seen on previous SERTS flights, which were measured with the highest spectral resolution (0.03 Å) ever achieved for spatially resolved active region spectra in this wavelength range. However, even at this high spectral resolution, several of the Fe XI lines are found to be blended, although the sources of the blends are identified in the majority of cases. The most useful Fe XI electron density diagnostic line intensity ratio is I(184.80 Å)/I(188.21 Å). This ratio involves lines close in wavelength and free from blends, and it varies by a factor of 11.7 between Ne = 109 and 1011 cm-3 yet shows little temperature sensitivity. An unknown line in the SERTS spectrum at 189.00 Å is found to be due to Fe XI, the first time (to our knowledge) this feature has been identified in the solar spectrum. Similarly, there are new identifications of the Fe XI 192.88, 198.56, and 202.42 Å features, although the latter two are blended with S VIII/Fe XII and Fe XIII, respectively.

Detections of molecular hydrogen in the outer filaments of NGC 1275

We present clear spectroscopic detections of molecular hydrogen in the outer filaments of the Ha nebula surrounding the central galaxy of the Perseus cluster, NGC 1275. This implies the presence of warm molecular gas clouds at projected distances up to 24 kpc from the nucleus of the host galaxy, embedded in the hot intracluster medium. The emission-line intensity ratios reveal that the H 2 is predominately thermally excited with excitation temperatures of 1600-2200 K, suggesting a lack of pressure balance between the molecular component and its surrounding medium. Excitation by stellar ultraviolet or by the central active galactic nucleus is shown to be unlikely, while thermal excitation by X-rays or conduction from the ICM or shocks are all possibilities. Evidence for a non-thermal component is found in the spectra of some regions based on a low ortho-to-para ratio.

Mode transitions in low pressure rare gas cylindrical ICP discharge studied by optical emission spectroscopy

We report optical emission spectroscopy (OES) measurements in cylindrical inductively coupled plasma (ICP) discharges, focusing on E-to-H mode transition in rare gases (Ar, Kr, Xe). The discharge configuration is designed primarily as a radical source for treatment in a high vacuum system, but little is known about its characteristics. Two discharge modes are observed in Ar and Kr on increasing the power injected into the discharge (E-mode at low injected power and H-mode at high injected power). In this paper, we use OES measurements and calculations to infer rare gas discharge characteristics and mode transitions for this geometry in rare gases. It is shown that emission line intensity ratios from the OES signal of a level that is strongly coupled to a metastable state with one whose principal production mechanism is by direct excitation can be used to infer information about the electronic parameters of the discharge.

A Comparision of Theoretical Si VIII Emission Line Ratios with Observations from Serts

Recent R-matrix calculations of electron impact excitation rates in N-like Si VIII are used to derive theoretical emission line intensity ratios involving 2s22p3–2s2p4 transitions in the 216–320 A wavelength range. A comparison of these with an extensive dataset of solar active region, quiet-Sun, sub-flare and off-limb observations, obtained during rocket flights of the Solar EUV Research Telescope and Spectrograph (SERTS), indicates that the ratio R1= I(216.94 A)/I(319.84 A) may provide a usable electron density diagnostic for coronal plasmas. The ratio involves two lines of comparable intensity, and varies by a factor of about 5 over the useful density range of 108–1011 cm−3. However R2= I(276.85 A)/I(319.84 A) and R3=I(277.05 A)/I(319.84 A) show very poor agreement between theory and observation, due to the severe blending of the 276.85 and 277.05 A lines with Si VII and Mg VII transitions, respectively, making the ratios unsuitable as density diagnostics. The 314.35 A feature of Si VIII also appears to be blended, with the other species contributing around 20% to the total line flux.

Electronic structure and thermoelectric properties of skutterudite compounds

We present soft x-ray fluorescence measurements of skutterudite compounds(CoAs3 and CoSb3). Our results are compared with x-ray photoelectron spectra (XPS) and band structurecalculations. The occupancy of d states is found to increase in transition metalantimonides with respect to that of pure metals. The experimental spectra areinterpreted in terms of our LDA band structure calculations and we find that electroncorrelation does not have to be taken into account. The intensity ratio of the CoL2 toL3 emission lines is found to be 0.20 and 0.15 forCoAs3 and CoSb3, respectively, which we attribute to the decrease in Coster–Kronig processes inCoAs3 comparedto CoSb3 with its smaller carrier density. The calculated values of the thermoelectric figures of merit show thatCoSb3 is the most promising thermoelectric material, which is in accordance with experimentalmeasurements of the electrical conductivity and Seebeck coefficient.

Extreme‐Ultraviolet Emission Lines of Sxin Solar Flare and Active Region Spectra

R-matrix calculations of electron impact excitation rates in N-like S X are used to derive theoretical emission-line intensity ratios involving 2s22p3-2s2p4 transitions in the 189-265 A wavelength range. A comparison of these with observational data for solar flares and active regions, obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab and the Solar EUV Rocket Telescope and Spectrograph, reveals that many of the S X lines in the spectra are badly blended with emission features from other species. However, the intensity ratios I(228.70 A)/I(264.24 A) and I(228.70 A)/I(259.49 A) are found to provide useful electron density diagnostics for flares, although the latter cannot be employed for active regions, because of blending of the 259.49 A line with an unidentified transition in these solar features.