Ionic Lines Research Articles

Screening and relativistic effects on the stark broadening of hydrogenic ion lines in a plasma

In the present work, we compute the amplitude of the real part of the electronic collision operator for the electron broadening of hydrogenic ion lines in plasmas, taking into account the screening effects (the interaction between the free electron (perturber) and the ion (emitter) is governed by Debye potential) and relativistic effects in the dynamics of the perturbing electron. The screening effects are included using the cross section calculated by Debye potential instead of Rutherford cross section and the relativistic effects are included by the modification of the velocity distribution (Maxwell–Jûttner) instead of (Maxwell–Boltzmann) distribution and relativistic mass (mass depend on the velocity). The obtained results are compared with Griem’s theoretical work.

Plasma diagnosis inside the discharge channel of a low-power Hall thruster working on Xe/Kr mixtures

In this paper, optical diagnostics for the internal plasma of a low-power Hall thruster working on Xe/Kr mixtures is carried out. The emission spectroscopy results show that the atomic and ionic spectral lines reach the maximum at 5 mm and 3 mm upstream of the channel exit, respectively, indicating a spatial separation between atom excitation and ionization. The krypton atomic spectral intensity obtains the maximum closer to the channel exit than xenon. Presence of xenon is demonstrated to substantially increase the density of krypton atoms in metastable state and promote the ionization of krypton atoms. Both the enhanced mixture flowrate and Kr fraction push the ionization zone downstream. Increases in discharge voltage and discharge channel length shift the ionization zone upstream. For the overall performance, a longer discharge channel improves the thrust efficiency. It is mainly attributed to a more focused plume, an increase in the current efficiency from 80% to 84%, and a reduction in the electron current of about 28.57%. Therefore, under the condition of further optimized channel erosion issue, an extended discharge channel is recommended in the practical tests of Xe/Kr mixtures to compensate for the inefficiencies caused by krypton atoms.

Precision Measurements of X-Ray Spectra for the Diagnosis of Laboratory Astrophysical Plasma

A technique is described for achieving high accuracy (relative error up to ≈0.001%) for measuring the absolute wavelengths of the spectral lines of multiply charged ions with an average (Z = 17–25) by the nuclear charge, the spectra of which can be used for plasma diagnostics in laboratory astrophysics experiments. It is based on irradiation with subnanosecond laser pulses with an intensity of 1015–1016 W/cm2 targets with a multicomponent chemical composition, including atoms with both medium and low Z. The presence of the latter ensures the presence in the emission spectrum of the resulting laser plasma of lines of hydrogen-like ions used as references. An atomic-kinetic code was created, and the intensities of possible reference and investigated spectral lines were calculated. The principles of selecting the target material, the features of the implementation of the technique on the example of a focusing spectrometer with spatial resolution based on spherically curved mica and α-quartz crystals are considered, and specific parameters of spectrometer circuits and types of targets for precision measurement of the wavelengths of spectral lines of helium- and lithium-like ions with nuclear charges Z = 13–25 are given. The results obtained in this work will be used in the planning of fundamental X-ray spectral studies at the ELF laser facility being developed at MEPhI.

General expression for the probability distribution function of electric field in a spatially inhomogeneous non-neutral plasma

We discuss the influence of micro- and macro-fields on spectral lines of ions as it takes place for spatially inhomogeneous plasma. A distribution function of an electric field is obtained. The function accounts for inhomogeneity and non-neutrality of plasma. The results of calculations of this function for various regimes are presented. Experimental results for ultracold plasma are used to compare theory with experiment. Dependence of the absorption coefficient on the function is shown. These results may be useful for diagnostics of various types of plasmas. One of the methods of plasma diagnostics is the analysis of the influence of its electric field on the shape of the spectral lines of atoms and ions (the Stark effect).

Statistical analysis of Al III and C III] emission lines as virial black hole mass estimators in quasars

Aims. We test the usefulness of the intermediate ionisation lines Al IIIλ1860 and C III]λ1909 as reliable virial mass estimators for quasars. Methods. We identified a sample of 309 quasars from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16) in the redshift range 1.2 ≤ z ≤ 1.4 that have [O II]λ3728 recorded on the same spectrum as Al IIIλ1860, Si III]λ1892, and C III]λ1909. We set the systemic quasar redshift using careful measurements of [O II]λ3728. We then classified the sources as Population A (Pop. A), extreme Population A (Pop. xA), and Population B (Pop. B), and analysed the 1900 Å blend using multi-component models to look for systematic line shifts of Al IIIλ1860 and C III]λ1909 along the quasar main sequence. Results. We do not find significant shifts of the Al IIIλ1860 line peak in Pop. B or in the vast majority of Pop. A. For Pop. xA, a small median blueshift of −250 km s−1 was observed, motivating a decomposition of the Al III line profile into a virialised component centred at rest frame and a blueshifted component for an outflow emission. For Pop. B objects, we proved the empirical necessity to fit a redshifted very broad component, clearly seen in C III], and analysed the physical implications on a Pop. B composite spectrum using CLOUDY simulations. We find consistent black hole mass estimations using Al III and C III] as virial estimators for the bulk of Pop. A. Conclusions. Al III (and even C III]) is a reliable virial black hole mass estimator for Pop. A and Pop. B objects. The Pop. xA sources deserve special attention due to the significant blueshifted excess observed in the line profile of Al III, although it is not as large as the excess observed in C IVλ1549.

The obscured nucleus and shocked environment of VV 114E revealed by JWST/MIRI spectroscopy

ABSTRACT Compact Obscured Nuclei (CONs) potentially hide extreme supermassive black hole (SMBH) growth behind large column densities of gas/dust. We present a spectroscopic analysis of the heavily obscured nucleus and the surrounding environment of the eastern region of the nearby (z = 0.02007) interacting galaxy VV 114 with the JWST Mid-InfraRed Instrument (MIRI). We model the spectrum from 4.9 to 28 μm to extract polycyclic aromatic hydrocarbon (PAH) emission and the underlying obscured continuum. We find that the NE nucleus (A) is highly obscured where the low PAH equivalent width (EW) ratio, EW(12.7)/EW(11.3), reveals a dust enshrouded continuum source. This is confirmed by decomposing the continuum into nuclear and star-forming where the nuclear component is found to be typical of CONs. The 11.3/6.2 PAH flux ratio is consistent with originating in star-forming regions rather than typical AGN. The second nucleus (B) is much less obscured, with PAH flux ratios also typical of star-forming regions. We do not detect any high ionization lines such as [Ne v] or [Ne vi] which suggests that if an AGN is present it must be highly obscured. Additionally, we detect a shock front south of the secondary nucleus (B) in the [Fe ii] (5.34 μm) line and in warm molecular hydrogen. The 6.2 PAH emission does not spatially coincide with the low-J transitions of H2 but rather appears strong at the shock front which may suggest destruction of the ionized PAHs in the post-shock gas behind the shock front.

Spectral analysis of the AMXP IGR J17591–2342 during its 2018 outburst

ABSTRACT The Accreting Millisecond X-ray Pulsar IGR J17591–2342 is a Low Mass X-ray Binary (LMXB) system that went in outburst on 2018 August and it was monitored by the NICER observatory and partially by other facilities. We aim to study how the spectral emission of this source evolved during the outburst by exploiting the whole X-ray data repository of simultaneous observations. The continuum emission of the combined broad-band spectra is on average well described by an absorbed Comptonization component scattering blackbody-distributed photons peaking at (0.8 ± 0.5) keV by a moderately optically thick corona (τ = 2.3 ± 0.5) with temperature of (34 ± 9) keV. A blackbody component with temperature and radial size of (0.8 ± 0.2) keV and (3.3 ± 1.5) km, respectively, is required by some of the spectra and suggests that part of the central emission, possibly a fraction of the neutron star surface, is not efficiently scattered by the corona. The continuum at low energies is characterized by significant residuals suggesting the presence of an absorption edge of O viii and of emission lines of Ne ix ions. Moreover, broad Fe i and Fe xxv Kα emission lines are detected at different times of the outburst, suggesting the presence of reflection in the system.

Time-evolution characteristics of spectrum and temperature of lightning discharge plasma

Temperature is one of the crucial parameters reflecting the energy and current transfer characteristics in lightning discharge plasma channels. According to the spectra of six lightning return strokes discharges recorded simultaneously by two high-speed slit-less spectrographs with different time resolutions, the spectral intensity and temperature evolution of the plasma channels over time was quantitatively analyzed. The spectral characteristics show that the ionic line intensity decayed rapidly with time as the current declined, while the atomic line intensity decreased more slowly. Additionally, it is found that the ionic lines existed for a much longer time than previously reported values, up to hundreds of microseconds in the spectra of continuing current process. It further indicates that the ionic line intensities are associated with the discharge currents and that their radiation mechanisms are closely related to the collision excitation under the action of strong currents. The temperature calculated by the ionic lines can reflect the thermodynamic properties of the current-carrying channel. The temperature calculated using atomic lines is significantly lower than that calculated by the ionic lines in the same spectrum. The radiation mechanism for a majority of the atomic lines differs from that of the ionic lines. During the continuing current, the channel temperatures calculated by both ionic and atomic lines showed a similar evolution feature which declined slowly or even remained basically unchanged. This property reflects the persistent heating effect of the current.

The Role of the Spectral Lines of Atoms and Ions in Radiative Heating of the Surfaces of Space Capsules

The Role of the Spectral Lines of Atoms and Ions in Radiative Heating of the Surfaces of Space Capsules

Core-resonance line-shape analysis of atoms undergoing strong-field ionization

Using attosecond transient absorption spectroscopy for time delays where the near-infrared pump and the extreme ultraviolet (XUV) probe pulses overlap, sub-cycle structures in the build-up of absorption lines in xenon ions are investigated as a function of the pump intensity during strong-field ionization. We observe a half-cycle-periodic change in the line-shape asymmetry of the ionic 4d–5p resonances. Analyzing the line shapes, we find that in particular the phase of the induced dipole emission is modified, and the magnitude of this phase modulation decreases with increasing laser intensity. We discuss the influence of ground state depletion on interfering pathways involved in XUV-assisted strong-field ionization.

Theoretical study of excitation energies and radiative data with identification of SXR and EUV spectral lines for Li-like ions

Theoretical study of excitation energies and radiative data with identification of SXR and EUV spectral lines for Li-like ions

Study of spectral intensity of the laser ablated tungsten plasma and ablation mass at various laser spot sizes and laser fluence in vacuum environment

The ablation features such as spot size and crater volume are essential parameters for the in-situ laser-induced breakdown spectroscopy (LIBS) technique to be well applied in the quantitative diagnosis of the plasma-wall interaction (PWI) processes on the first wall or divertor in tokamak devices. The spectroscopic characteristics and the ablation features as well as the plume dynamics of laser-induced tungsten plasma in vacuum environment at various spot sizes were investigated in this work. A nano-second laser pulse (5 ns, 1064 nm) with a maximum energy of 200 mJ was focused on the tungsten target with different spot sizes (from 0.42 mm to 2.71 mm) by adjusting the distance from focal point to sample surface. A paraxially collective configuration (15°) and time-integrated spectral collection mode were applied, similar to the present in-situ LIBS system on Experimental Advanced Superconducting Tokamak (EAST). It was observed that the spot size affects the spectral intensity significantly, and the optimal spot size is 1.16 mm both for the observed tungsten ionic and atomic lines at the laser energy of 200 mJ. The electron temperature (Te), electron density (ne) and ablation mass also reach maxima at the optimal spot size. Temporally spectral dynamic investigation shows the tungsten line emission time at the optimal spot size lasts longer and decays more slowly than other sizes, and the fast photography investigation also verified this. It was found that the central intensity profile of the plasma plume image from the target surface along with the opposite direction of the laser incident at the early stage (< 8 ns, during the laser pulse) is stronger at the smaller spot size while it decays faster. This was attributed to the stronger plasma shielding effect leading to the relatively less total ablation mass. Moreover, the optimal spot size was found to increase with the laser energy in the energy range from 65 mJ to 200 mJ, and the corresponding optimal laser fluence almost keeps the constant value of ∼18 J/cm2, which provides valuable information for optimizing the current in-situ LIBS for quantitative diagnosis of the PWI processes such as fuel retention and impurity deposition in EAST.

Comparison of heating mechanisms of argon helicon plasma in different wave modes with and without blue core

In this work, we investigated the discharge characteristics and heating mechanisms of argon helicon plasma in different wave coupled modes with and without blue core. Spatially resolved spectroscopy and emission intensity of argon atom and ion lines were measured via local optical emission spectroscopy, and electron density was measured experimentally by an RF-compensated Langmuir probe. The relation between the emission intensity and the electron density was obtained and the wavenumbers of helicon and ‘Trivelpiece-Gould’ (TG) waves were calculated by solving the dispersion relation in wave modes. The results show that at least two distinct wave coupled modes appear in argon helicon plasma at increasing RF power, i.e. blue core (or BC) mode with a significant bright core of blue lights and a normal wave (NW) mode without blue core. The emission intensity of atom line 750.5 nm (I ArI750.5nm) is related to the electron density and tends to be saturated in wave coupled modes due to the neutral depletion, while the intensity of ion line 480.6 nm (I ArII480.6nm) is a function of the electron density and temperature, and increases dramatically as the RF power is increased. Theoretical analysis shows that TG waves are strongly damped at the plasma edge in NW and/or BC modes, while helicon waves are the dominant mechanism of power deposition or central heating of electrons in both modes. The formation of BC column mainly depends on the enhanced central electron heating by helicon waves rather than TG waves since the excitation of TG waves would be suppressed in this special anti-resonance region.

Properties of the interstellar medium in star-forming galaxies at redshifts 2 ≤ z ≤ 5 from the VANDELS survey

Gaseous flows inside and outside galaxies are key to understanding galaxy evolution, as they regulate their star formation activity and chemical enrichment across cosmic time. We study the interstellar medium (ISM) kinematics of a sample of 330 galaxies with C III] or He II emission using far-ultraviolet (far-UV) ISM absorption lines detected in the ultra deep spectra of the VANDELS survey. These galaxies span a broad range of stellar masses from 108 to 1011 M⊙, and star formation rates (SFRs) from 1 to 500 M⊙ yr−1 in the redshift range between 2 and 5. We find that the bulk ISM velocity along the line of sight (vIS) is globally in outflow, with a vIS of −60 ± 10 km s−1 for low-ionisation gas traced by Si IIλ1260 Å, C IIλ1334 Å, Si IIλ1526 Å, and Al IIλ1670 Å absorption lines, and a vIS of −160 ± 30 and −170 ± 30 km s−1 for higher ionisation gas traced respectively by Al IIIλλ1854-1862 Å and Si IVλλ1393-1402 Å. Interestingly, we notice that BPASS models are able to better reproduce the stellar continuum around the Si IV doublet than other stellar population templates. For individual galaxies, 34% of the sample has a positive ISM velocity shift, almost double the fraction reported at lower redshifts. We additionally derive a maximum outflow velocity vmax for the average population, which is of the order of ∼ − 500 and ∼ − 600 km s−1 for the lower and higher ionisation lines, respectively. Comparing vIS to the host galaxies properties, we find no significant correlations with stellar mass M⋆ or SFR, and only a marginally significant dependence (at ∼2σ) on morphology-related parameters, with slightly higher velocities found in galaxies of smaller size (probed by the equivalent radius rT50), higher concentration (CT), and higher SFR surface density ΣSFR. From the spectral stacks, vmax shows a similarly weak dependence on physical properties (at ≃2σ). Moreover, we do not find evidence of enhanced outflow velocities in visually identified mergers compared to isolated galaxies. From a physical point of view, the outflow properties are consistent with accelerating momentum-driven winds, with densities decreasing towards the outskirts. Our moderately lower ISM velocities compared to those found in similar studies at lower redshifts suggest that inflows and internal turbulence might play an increased role at z &gt; 2 and weaken the outflow signatures. Finally, we estimate mass-outflow rates Ṁout that are comparable to the SFRs of the galaxies (hence a mass-loading factor η of the order of unity), and an average escape velocity of 625 km s−1, suggesting that most of the ISM will remain bound to the galaxy halo.

Effect of spatial distribution of impurity ions on the signal of ‘C/O monitor for Wendelstein 7-X’ - an indicator of plasma wall interactions

• A forward modelling was applied to investigate the response of the C/O monitor system; • Simulations were performed for Lyman-α lines of H-like ions of carbon and oxygen; • The analysis covered studies of impact of impurity transport on the output signals. • Systems' response on radial impurity distribution depends on the measured element. • Modelling should always be included during analysis of experimental data. The ‘C/O monitor’ is a dedicated diagnostic system designed to monitor light impurities (B, C, N and O) in the Wendelstein 7-X (W7-X) stellarator. Its main goal is to provide fast (∼1 ms) information about the impurity level which is measured from a large plasma volume (high throughput). Its first subsystem dedicated to measure Lyman-α lines of H-like carbon (C5+ − 3.4 nm – used as PFC material) and oxygen (O7+ − 1.9 nm – common impurity absorbed by inner vessels’ walls) is going to be commissioned during the next Operational Phase of W7-X. Since the radiated photon intensity of a given impurity depends strongly on plasma kinetic parameters (T e , n e ) and impurity transport, it is important to thoroughly understand the underlying correlation between these factors and registered signal. Because the dependences turn out to be non-trivial, a forward modelling was applied. This paper outlines the results of Lyman-α line intensities modelling performed for carbon and oxygen studies (including impurity transport), as only those two elements will be measured during the initial operational phase of the spectrometer. The obtained results indicates that the signals measured by the system will be weakly dependant on the plasma conditions.

Calculation of Radiative Properties for [82%Ar-18%CO2]-Fe Plasmas in MAG Welding Arc.

This paper is dedicated to the calculation of the radiative properties of 82%argon-18%CO2 thermal plasmas with the addition of metallic vapors (iron, in the present case, due to workpiece and wire erosion), this mixture being representative of metal active gas (MAG) arc welding processes. These radiative properties are obtained in the frame of the net emission coefficient (NEC) theory, using the recent and accurate “line by line” method. All significant radiative contribution mechanisms are taken into account in the calculation: atomic lines, atomic continuum (radiative attachment, radiative recombination, and bremsstrahlung), molecular bands for diatomic and polyatomic molecules, and molecular continuum. Broadening phenomena (Doppler and pressure effects) are also carefully treated for bound-bound transitions (atomic lines and molecular bands). Regarding 82%Ar-18%CO2 plasma, the results obtained demonstrate the key role of molecular bands at low temperatures (T < 4 kK), whereas the atomic line and continuum prevailed at intermediate and high temperatures. With the addition of a few percentages of iron vapor, it was shown that the total NEC is significantly increased (especially at low temperatures) and that the atomic and ionic lines become dominant in all the studied temperature ranges (3–30 kK). This theoretical study will constitute a groundwork to build a diagnostic method (based on the calculation of partial NECs for accurately chosen spectral intervals) for the determination of plasma temperature and iron vapor concentration in welding arcs.

Vibrational Emission Study of the CN and C2 in Nylon and ZnO/Nylon Polymer Using Laser-Induced Breakdown Spectroscopy (LIBS).

The laser-induced breakdown spectroscopy (LIBS) technique was performed on polymers to study the neutral and ionic emission lines along with the CN violet system (B2Σ+ to X2Σ+) and the C2 Swan system (d3 Пg–a3 Пu). For the laser-based emission analyses, the plasma was produced by focusing the laser beam of a Q-switched Nd: YAG laser (2ω) at an optical wavelength of 532 nm, 5 ns pulse width, and a repetition frequency of 10 Hz. The integration time of the detection system was fixed at 1–10 ms while the target sample was positioned in air ambiance. Two organic polymers were investigated in this work: nylon and nylon doped with ZnO. The molecular optical emission study of nylon and doped nylon polymer sample reveals CN and C2 molecular structures present in the polymer. The vibrational emission analysis of CN and C2 bands gives information about the molecular structure of polymers and dynamics influencing the excitation structures of the molecules. Besides, it was further investigated that the intensity of the molecular optical emission structure strongly depends on the electron number density (cm−3), excitation temperature (eV), and laser irradiance (W/cm2). These results suggest that LIBS is a reliable diagnostic technique for the study of polymers regarding their molecular structure, identification, and compositional analysis.

Warm molecular and ionized gas kinematics in the type-2 quasar J0945+1737

We analyse Near-Infrared Integral Field Spectrograph (NIFS) observations of the type-2 quasar (QSO2) SDSS J094521.33+173753.2 to investigate its warm molecular and ionized gas kinematics. This QSO2 has a bolometric luminosity of 1045.7 erg s−1 and a redshift of z = 0.128. The K-band spectra provided by NIFS cover a range of 1.99–2.40 μm where low ionization (Paα and Brδ), high ionization ([S XI]λ1.920 μm and [Si VI]λ1.963 μm), and warm molecular lines (from H21-0S(5) to 1-0S(1)) are detected, allowing us to study the multi-phase gas kinematics. Our analysis reveals gas in ordinary rotation in all the emission lines detected and also outflowing gas in the case of the low and high ionization emission lines. In the case of the nuclear spectrum, which corresponds to a circular aperture of 0.3″ (686 pc) in diameter, the warm molecular lines can be characterized using a single Gaussian component of full width at half maximum (FWHM) = 350 − 400 km s−1, while Paα, Brδ, and [Si VI] are best fitted with two blue-shifted Gaussian components of FWHM ∼ 800 and 1700 km s−1, in addition to a narrow component of ∼300 km s−1. We interpret the blue-shifted broad components as outflowing gas, which reaches the highest velocities, of up to −840 km s−1, in the south-east direction (PA ∼ 125°), extending up to a distance of ∼3.4 kpc from the nucleus. The ionized outflow has a maximum mass outflow rate of Ṁout,max = 42–51 M⊙ yr−1, and its kinetic power represents 0.1% of the quasar bolometric luminosity. Very Large Array (VLA) data of J0945 show extended radio emission (PA ∼ 100°) that is aligned with the clumpy emission traced by the narrow component of the ionized lines up to scales of several kiloparsecs, and with the innermost part of the outflow (central ∼0.4″ = 915 pc). Beyond that radius, at the edge of the radio jet, the high velocity gas shows a different PA of ∼125°. This might be an indication that the line-emitting gas is being compressed and accelerated by the shocks generated by the radio jet.

Initial Ionospheric Ion Line Results and Evaluation by Sanya Incoherent Scatter Radar (SYISR)

AbstractA new incoherent scatter radar (ISR) has recently been dedicated at Sanya (SYISR), China (geographic 18.34°N and 109.62°E) to detect the low‐latitude ionospheric plasma by conducting continuous operation and electronic beam steering on a pulse‐to‐pulse basis. This paper provides an overview of the processing procedure of SYISR ion line data and presents some preliminary observational results under various transmitting signal schemes and different working modes, such as the zenith‐directed mode and meridional and zonal scanning modes, with comparison to the international reference ionosphere model (IRI‐2016), ionosonde and Ionospheric Connections Explorer (ICON) satellite measurements. The diurnal and altitude versus latitude variation characteristics of electron density (Ne), electron temperature (Te), and ion temperature (Ti) are in accordance with those of other ISR measurements in mid‐low latitudes, and IRI shows some discrepancies with SYISR observations, including the sunrise and sunset enhancement in SYISR_Ti and the overestimated IRI_Te. The comparison between the daytime SYISR_Ti and ICON_Ti shows good consistency based on 31 observational samples. The measurement of line‐of‐sight velocity (Vi) for long pulse can reveal the properties of the medium scale traveling ionospheric disturbances manifesting the radar's potential to study the mesoscale ionospheric variation in the Sanya area. The derived vector velocities with a better measurement accuracy during the day are generally in line with ionospheric plasma physics. The results show that SYISR can obtain continuous ionospheric parameters through multi‐beam scanning measurements at ∼700 km horizontal scale, which provides important information for studying the atmosphere‐ionosphere‐magnetosphere coupling and ionospheric scintillation at low latitudes in East Asia.

Pre-heating of an aluminum sample using a continuous laser diode in LIBS experiments

We present here the study of the pre-heating of an aluminum sample in laser-induced plasma spectroscopy (LIBS) experiments. The pre-heating of the sample was made using a continuous-wave (CW) laser diode having a wavelength of 450nm and 3.8 W power. The laser diode is focused on the aluminum sample by means of a plane-convex lens with a focal length of 10 cm. The ablation plasma is created by a pulsed Nd:YAG laser with 7ns of pulse duration. The results of using different energy values per pulse of the ablation laser on the pre-heated sample are reported. The pre-heating of the aluminum sample, using this laser diode, shows an increment of 30-50% in the ionic line intensity.