Forbidden Components Research Articles

Measurement of the Plasma Density of the Current Sheet by the Broadening of the Spectral Lines of Atomic Helium He I 447.1 and 492.2 nm with Forbidden Components

Measurement of the Plasma Density of the Current Sheet by the Broadening of the Spectral Lines of Atomic Helium He I 447.1 and 492.2 nm with Forbidden Components

Hydrogen Line Shapes in Plasmas with Large Magnetic Fields

We report on hydrogen line shape calculations in the presence of an external magnetic field, at conditions such that the quadratic Zeeman effect is important. The latter is described through a term proportional to B2 in the Hamiltonian, accounting for atomic diamagnetism. It provides a shift and an asymmetry on Lorentz triplets, and it leads to the occurrence of forbidden components. Motivated by investigations performed at the fifth edition of the Spectral Line Shape in Plasmas (SLSP5) code comparison workshop, we perform new calculations of hydrogen Lyman line profiles. Field values representative of magnetized white dwarf atmosphere conditions are taken. The calculations are done using a computer simulation technique, designed for Stark broadening modeling. A discussion of the results is done in the framework of plasma diagnostics.

Computational and Spectroscopic Studies of Carbon Disulfide.

The vibrational spectroscopy of CS2 has been investigated many times in all three phases. However, there is still some ambiguity about the location of two of the modes in the solid state. The aim of this work was to locate all of the modes by inelastic neutron scattering (INS) spectroscopy, (which has no selection rules), and to use periodic density functional theory to provide a complete and unambiguous assignment of all the modes in the solid state. A comparison of the observed and calculated INS spectra shows generally good agreement. All four of the ν2 bending mode components are calculated to fall within 14 cm−1. Inspection of the spectrum shows that there are no bands close to the intense feature at 390 cm−1 (assigned to ν2); this very strongly indicates that the Au mode is within the envelope of the 390 cm−1 band. Based on a simulation of the band shape of the 390 cm−1 feature, the most likely position of the optically forbidden component of the ν2 bending mode is 393 ± 2 cm−1. The calculations show that the optically inactive Au translational mode is strongly dispersed, so it does not result in a single feature in the INS spectrum.

Forbidden component of the Be II 436.1 nm line recorded from pulsed gas discharge plasma

We report results of the experimental study of the singly charged beryllium spectral line 436.1 nm, transition , and forbidden component, transition , which is for the first time identified in this work. Beryllium lines are recorded from gas discharge, after ablation of a beryllium oxide discharge tube, running in pulsed regime with the following gases: helium with traces of hydrogen, argon with traces of hydrogen and pure krypton. The ratio of line intensities and wavelength separation of the Be II 436.1 nm line and neighbouring line located at the blue wing are followed in the electron density range (1.16–6.4) × 1022 m−3 determined from the hydrogen Balmer beta line () in the electron temperature interval between 10500 K and 15500 K. The functional dependence of the wavelength separation range and peak intensity ratio of these lines upon electron number density suggests the complex profile of the forbidden and allowed line, which can be used for diagnostics of low-temperature beryllium containing plasmas.

Study of Stark broadening of Li i 460 and 497 nm spectral lines with independent plasma diagnostics by Thomson scattering

We present results of experimental and theoretical studies of the Stark broadening of the Li i 460 nm spectral line with forbidden components and of the isolated 497 nm line. Plasma was induced by Nd:YAG laser radiation at 1064 nm with pulse duration ∼4.5 ns. Laser-induced plasma was generated in front of the alumina pellet, with some content of Li2CO3, placed in a vacuum chamber filled with argon under reduced pressure. Plasma diagnostics was performed using the laser Thomson scattering technique, free from assumptions about the plasma equilibrium state and its composition and so independently of plasma emission spectra. Spatially resolved spectra with Li lines were obtained from the measured, laterally integrated ones applying the inverse Abel transform. The Stark profiles were calculated by computer simulation method assuming a plasma in the local thermodynamic equilibrium. Calculations were performed for experimentally-inferred electron densities and temperatures, from 1.422 × 1023 to 3.55 × 1022 m−3 and from 1.96 eV to 1.04 eV, respectively. Our studies show very good agreement between experimental Stark profiles and those computer simulated.

Quantitative spectroscopy of extreme helium stars Model atmospheres and a non-LTE abundance analysis of BD+10°2179

Extreme helium stars (EHe stars) are hydrogen-deficient supergiants of spectral type A and B. They are believed to result from mergers in double degenerate systems. In this paper we present a detailed quantitative non-LTE spectral analysis for BD+10$^\circ$2179, a prototype of this rare class of stars, using UVES and FEROS spectra covering the range from $\sim$3100 to 10 000 {\AA}. Atmosphere model computations were improved in two ways. First, since the UV metal line blanketing has a strong impact on the temperature-density stratification, we used the Atlas12 code. Additionally, We tested Atlas12 against the benchmark code Sterne3, and found only small differences in the temperature and density stratifications, and good agreement with the spectral energy distributions. Second, 12 chemical species were treated in non-LTE. Pronounced non-LTE effects occur in individual spectral lines but, for the majority, the effects are moderate to small. The spectroscopic parameters give $T_\mathrm{eff}$ = 17 300$\pm$300 K and $\log g$ = 2.80$\pm$0.10, and an evolutionary mass of 0.55$\pm$0.05 $M_\odot$. The star is thus slightly hotter, more compact and less massive than found in previous studies. The kinematic properties imply a thick-disk membership, which is consistent with the metallicity $[$Fe/H$]\approx-1$ and $\alpha$-enhancement. The refined light-element abundances are consistent with the white dwarf merger scenario. We further discuss the observed helium spectrum in an appendix, detecting dipole-allowed transitions from about 150 multiplets plus the most comprehensive set of known/predicted isolated forbidden components to date. Moreover, a so far unreported series of pronounced forbidden He I components is detected in the optical-UV.

A high spectral resolution map of the nuclear emitting regions of NGC 7582

We present the results of the spatial and spectral analysis of the deep (~200 ksec) Chandra HETG observation of the changing look AGN NGC7582. During this observation NGC7582 was in a highly obscured state. Therefore, we considered also a short Suzaku observation, which caught NGC7582 in a Compton thick state. This allows us to determine the underlying continuum and the amount of absorption ($N_H \sim~1.2\times10^{24}$ cm$^{-2}$). A wealth of emission lines are detected in the Chandra data, which allow us to map the structure of the circum-nuclear emitters. The high resolution spectrum reveals that the soft X-ray emission originates in a hybrid gas, which is ionized in part by the starforming activity and in part by the central AGN. The high resolution images confirm that the emitting region is inhomogeneous and extends up to a few hundred pc from the nuclear source. The X-ray images are more extended in the lower energy lines (Ne and Mg) than in the higher energy lines (Si, Fe), where the former are dominated by the collisionally ionised gas and the latter by the photoionized AGN emission. This is supported by the analysis of the He-like triplets. We deduce that a low density photoionized gas is responsible for the strong forbidden components, which is likely to originate from extended AGN Narrow Line Region gas at distances of 200-300 pc from the black hole. We also detected an absorption feature at ~ 6.7 keV consistent with the rest frame energy of the resonance absorption line from FeXXV, which traces the presence of a sub-parsec scale ionized absorber. The emerging picture is in agreement with our view of the circumnuclear gas in AGN, where the medium is clumpy and stratified in both density and ionization. These absorbers and emitters are located on different scales: from the sub-pc Broad Line Region gas out to the kpc scale of the galactic absorber.

Halal integrity in the food supply chain

PurposeThis paper argues that there is an absence of halal integrity within the conventional stages of a food chain. This paper adapts the understanding of the different stages and argues the need to develop a critical consciousness for halal integrity within the food chain to address the needs of the ever-growing Muslim consumers’ market. The purpose of this paper is to propose a definition of halal integrity using farm to fork and global food supply chain models.Design/methodology/approachThe study includes a review of priori literature and media reports regarding cross-contamination of food products with haram (forbidden) components. This background will be used to conceptualise halal integrity using farm to fork and global supply chain models.FindingsDifferent interpretations of halal – what is permitted and what is prohibited – exist for the different schools of Islamic legal thought and within the customs of different countries. In order to ensure that food production is embracive of the religious needs of the global Muslim customer market, this paper utilises the farm to fork and global supply chain models to foster a critical awareness of halal needs. Halal integrity should be clearly presenting the details of the halal status of the product and assuring that the requirements for halal as stated are met. Halal integrity not only deals with permitted and prohibited foods, but that the halal status of the food products (i.e. from raw materials until it reaches the consumers) should not be breached (i.e. no cross-contamination with haram products/methods and no ill intents). A formal definition of halal integrity has been proposed.Research limitations/implicationsThe SWOT analyses serve as a guideline as the analysis done may be outdated as the environments are constantly changing.Originality/valueThis research although academic is meant to have a real value in improving the integrity of the halal food supply chain, providing value to the food industry, to countries that are concerned about this supply chain and to Muslim consumers. Halal integrity is crucial to the success of the emerging halal market.

DETECTION OF FORBIDDEN LINE COMPONENTS OF LITHIUM-LIKE CARBON IN STELLAR SPECTRA

ABSTRACT We report the first identification of forbidden line components from an element heavier than helium in the spectrum of astrophysical plasmas. So far, these components were identified only in laboratory plasmas and not in astrophysical objects. Forbidden components are well known for neutral helium lines in hot stars, particularly in helium-rich post-AGB stars and white dwarfs. We discovered that two hitherto unidentified lines in the ultraviolet spectra of hot hydrogen-deficient (pre-) white dwarfs can be identified as forbidden line components of triply ionized carbon (C iv). The forbidden components (3p–4f and 3d–4d) appear in the blue and red wings of the strong, Stark broadened 3p–4d and 3d–4f lines at 1108 Å and 1169 Å, respectively. They are visible over a wide effective temperature range (60,000–200,000 K) in helium-rich (DO) white dwarfs and PG 1159 stars that have strongly oversolar carbon abundances.

Stability of simultaneously block triangularisable switched systems with partial state reset

ABSTRACTWe study the stability of a certain class of switched systems where discontinuous jumps (resets) on some of the state components are allowed, at the switching instants. It is known that, if all components of the state are available for reset, the system can be stabilisable by an adequate choice of resets. However, this question may have negative answer if there are forbidden state components for reset. We give a sufficient condition for the stabilisability of a switched system, under arbitrary switching, by partial state reset in terms of a block simultaneous triangularisability condition. Based on this sufficient condition, we show that the particular class of systems with partially commuting stable system matrices is stabilisable by partial state reset. We also provide an algorithm that allows testing whether a switched system belongs to this particular class of systems.

The discharge for plasma Stark shift measurement and results for He I 706.522 nm line

We present results of Stark shift measurements for He I 706.522nm (1s2p 3P20–1s3s 3S1 and 1s2p 3P10–1s3s 3S1) lines using newly constructed pulsed arc generated at the pressure of two hundreds of milibars of helium with small admixture of hydrogen. Plasma electron number density in the range (0.5–7.0)×1023m−3 was measured from the wavelength separation between the allowed He I 447.1nm (2p 3P0–4d 3D) line and its forbidden component (2p 3P0–4d 3F0), while the electron temperature in the range (15,000–20,000)K was determined from the relative intensities of Si II lines using the Boltzmann plot technique. New Stark shift measurement technique was demonstrated using line shape recording of several He I lines. The shift results for He I 706.522nm line so favorably compare with earlier lower density experimental data that best fit formula is recommended for plasma diagnostic purposes.

Actual state and perspectives of Christian religious dietary laws and certification in Romania

Traditional foods tailored for religiously restricted menus represent up to a third of the Romanian food market during fasting and other religious periods, but food safety and enforcement organizations can only verify label declarations with products, without reference to the requirements imposed by the various Christian doctrines, 1 collectively still the largest religion in the world (ca. 2.5 billion people globally). A basic knowledge of food selection and restrictions associated with aspects of the Christian Church, described in Canon law, is crucial for food processing and certification as well as laws of fasting and abstinence practiced by believers throughout the liturgical year. Ideally, certification would include catering and restaurants, as well as specific events and tourism worldwide, and food companies should guarantee compliance with religious requirements to have value with consumers. Similarly, food authorities should provide – and be provided with – a checklist itemizing forbidden components and recommended procedures, which can be included in guidelines for manufacturers and retailers. Specific global and/or regional certification organization would avoid or reduce manufacture of counterfeit and/or fraudulent products, and strengthen positive perceptions of the commercial value and quality of certified products and services among relevant consumers. The present paper research aims to present the state-of-the-art and future trends regarding religious dietary laws and requirements for certification in the Romanian Orthodox Church food market.

Applied quantum chemistry: Spectroscopic detection and characterization of the F2BS and Cl2BS free radicals in the gas phase.

In this and previous work [D. J. Clouthier, J. Chem. Phys. 141, 244309 (2014)], the spectroscopic signatures of the X2BY (X = H, halogen, Y = O, S) free radicals have been predicted using high level ab initio theory. The theoretical results have been used to calculate the electronic absorption and single vibronic level (SVL) emission spectra of the radicals under typical jet-cooled conditions. Using these diagnostic predictions, the previously unknown F2BS and Cl2BS free radicals have been identified and characterized. The radicals were prepared in a free jet expansion by subjecting precursor mixtures of BF3 or BCl3 and CS2 vapor to an electric discharge at the exit of a pulsed molecular beam valve. The B̃(2)A1-X̃(2)B2 laser-induced fluorescence spectra were found within 150 cm(-1) of their theoretically predicted positions with vibronic structure consistent with our Franck-Condon simulations. The B̃(2)A1 state emits down to the ground state and to the low-lying Ã(2)B1 excited state and the correspondence between the observed and theoretically derived SVL emission Franck-Condon profiles was used to positively identify the radicals and make assignments. Excited state Coriolis coupling effects complicate the emission spectra of both radicals. In addition, a forbidden component of the electronically allowed B̃-X̃ band system of Cl2BS is evident, as signaled by the activity in the b2 modes in the spectrum. Symmetry arguments indicate that this component gains intensity due to a vibronic interaction of the B̃(2)A1 state with a nearby electronic state of (2)B2 symmetry.

Neutral lithium spectral line 460.28 nm with forbidden component for low temperature plasma diagnostics of laser-induced plasma

We present the results of theoretical and experimental line shape study of the Li I 460.28nm line with a forbidden component in a low temperature laser-induced plasma. For this purpose a computer simulation method is used to calculate the overall line profile in the electron number density range of (0.5–11.0)×1016cm-3 and the electron temperature 5800K. The same computer simulation method is used to evaluate asymmetric profiles of the isolated Li I 497.17nm line in the same electron density range and for several electron temperatures between 3500K and 10300K. The results for the Li I isolated line are used together with two other theoretical calculations for independent electron density measurements in laser induced plasma. The electron temperatures in the range of 4000–7000K were determined from relative Li I line intensities using Boltzmann plot technique. The comparison between calculated profiles and experimental data for the Li I 460.28nm line with a forbidden component indicates that theoretical results can be used for electron density diagnostics in the aforementioned density range with an accuracy of ±10–15%. To facilitate the application of theoretical line profiles simple expressions are supplied.

Stark broadening of the He I 492.2 nm line with forbidden components in dense low-temperature plasma

We present the results of an experimental study of the He I 492.2nm line with forbidden components emitted by low-electron temperature and high electron number density helium plasma with or without addition of hydrogen. The shapes of the He I 447.1nm and 501.6nm lines and hydrogen Hβ line were used to measure electron number density in the range (1–5)×1023m−3, while electron temperatures in the range from 25,000K to 35,000K were determined from the line to underlying continuum ratio of He I lines at 388.8, 667.8, 706.5 and 728.1nm. The experimental profiles of the He I lines are compared with the results of a computer simulation method. The comparison was performed by use of a program for simultaneous interpolation of data tables obtained by computer simulation for 492.2 and 501.6nm He I and hydrogen Hβ lines. The electron number densities obtained from this comparison agree within 10% with corresponding values determined from the 447.1nm He I line which is well within theoretical and experimental uncertainties for all lines included in comparison.

Stark broadening tables for the helium I 492.2 line

Context. We studied the Stark broadening of the He I 492.2 nm line, which is sometimes used for plasma diagnostics or to obtain information on different stellar parameters. Aims. The final aim of this study is to obtain tables of lines shapes as well as the relationships between different line parameters and the plasma electron density, temperature, or composition. The tables of profiles and the mathematical expressions obtained will be used in plasma diagnostics. Methods. We performed computer simulations and used a physical model that considers a weakly coupled plasma. Our computer simulations naturally take into account ion dynamical effects, which has permitted us to study the influence on the line shapes of imbalances in the plasma caused by different electron and gas temperatures. Results. Our computer simulations considered electron densities between 10 19 and 10 24 m −3 , electron temperatures between 5000 and 40 000 K, and plasmas of different compositions. The dependences obtained in the simulations for the line width, the ratio of intensities between the allowed and the forbidden components, or the distances between those components’ peaks on the plasma conditions are shown and compared with experimental data. Numerical expressions for the line width and for the peak distances against the electron density were obtained from the simulation results and can be applied to obtain the electron density from experimental results. Full line profile tables are also supplied for use in plasma diagnostics.

Polarized atomic radiative emission in electric and magnetic fields1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

A reduced density matrix approach is employed to provide a general theoretical description of polarized radiative emission during single-photon transitions from bound and auto-ionizing states of many-electron atomic systems in the presence of a general arrangement of static (or quasi-static) electric and magnetic fields. Polarized radiative emission from partially ionized atomic systems can occur as a result of the excitation of the radiating atomic states by electrons or ions with an anisotropic velocity distribution, which can be produced in an electron or ion beam experiment, and in a non-equilibrium plasma environment. Polarized radiative emission can also be produced or modified during the excitation of the atomic system in the presence of electric and magnetic fields, and electromagnetic fields. In electric and magnetic fields, the normally overlapping angular momentum projection components of atomic spectral lines can be substantially shifted from their field-free positions and split into spectroscopically resolvable (and inherently polarized) features. Because of the breakdown of the field-free angular momentum and parity selection rules, otherwise forbidden components of atomic spectral lines can be generated. Using a representation based on the field-free many-electron atomic states, the Stark–Zeeman patterns can be determined by a diagonalization of the atomic Hamiltonian in the presence of electric and magnetic fields. In the density operator approach, account can be taken of the coherent excitation of a particular subspace of the initial atomic bound or auto-ionizing states. A general expression for the matrix elements of the detected-photon density operator is obtained and provides a unified framework for the analysis of the spectral intensity, angular distribution, and polarization of the Stark–Zeeman patterns. From a unified development of time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations of the more comprehensive reduced density matrix approach, the non-equilibrium atomic state kinetics and the homogeneous spectral line shapes can be systematically and self-consistently described.

Plasma diagnostics using the He I 447.1 nm line at high and low densities

The broadening of the He I 447.1 nm line and its forbidden components in plasmas is studied using computer simulation techniques and the results are compared with our and other experiments. In these calculations wide ranges of electron densities and temperatures are considered. Experimental measurements are performed with a high electron density pulsed discharge and with a low electron density microwave torch at atmospheric pressure. Both calculations and experimental measurements are extended from previous works towards low electron densities in order to study the accuracy of plasma diagnostics using this line in ranges of interest in different practical applications. The calculation results are compared with experimental profiles registered in plasmas diagnosed using independent techniques. The obtained agreement justifies the use of these line parameters for plasma diagnostics. The influence of self-absorption on line parameters is also analysed. It is shown that the separation between the peaks of the allowed and forbidden components exhibits a clear dependence upon plasma electron density free of self-absorption influence. This allows the peak separation to be used as a good parameter for plasma diagnostics. From the simulation results, a simple fitting formula is applied that permits obtaining the electron number density plasma diagnostics in the range 5 × 1022–7 × 1023 m−3. At lower densities the fitting of simulated to experimental full profiles is a reliable method for Ne determination.

The X-ray spectral signatures from the complex circumnuclear regions in the Compton thick AGN NGC 424

We present the XMM-Newton RGS and EPIC pn spectra of a long (\simeq 100 ks) observation of one of the soft X-ray brightest Compton-thick Seyfert 2 galaxies, NGC 424. As a first step, we performed a phenomenological analysis of the data to derive the properties of all the spectral components. On the basis of these results, we fitted the spectra with self-consistent photoionisation models, produced with CLOUDY. The high-energy part of the spectrum is dominated by a pure neutral Compton reflection component and a neutral iron K-alpha line, together with K-alpha emission from neutral Ni, suggesting a significant Ni/Fe overabundance. The soft X-ray RGS spectrum comes mostly from line emission from H-like and He-like C, N, O, and Ne, as well as from the Fe L-shell. The presence of narrow RRC from O VIII, O VII, and C VI, the last two with resolved widths corresponding to temperatures around 5-10 eV, is a strong indication of a gas in photoionisation equilibrium, as confirmed by the prevalence of the forbidden component in the O VII triplet. Two gas phases with different ionisation parameters are needed to reproduce the spectrum with a self-consistent photoionisation model, any contribution from a gas in collisional equilibrium being no more than 10% of the total flux in the 0.35-1.55 keV band. When this self-consistent model is applied to the 0.5-10 keV band of the EPIC pn spectrum, a third photoionised phase is needed to account for emission lines with higher ionisation potential, although K-alpha emission from S XV and Fe XXVI remains under-predicted.

CHANDRAHIGH-RESOLUTION SPECTROSCOPY OF THE CIRCUMNUCLEAR MATTER IN THE BROAD-LINE RADIO GALAXY 3C 445

We present evidence for X-ray line emitting and absorbing gas in the nucleus of the Broad-Line Radio Galaxy (BLRG), 3C 445. A 200ks Chandra LETG observation of 3C 445 reveals the presence of several highly ionized emission lines in the soft X-ray spectrum, primarily from the He and H-like ions of O, Ne, Mg and Si. Radiative recombination emission is detected from O VII and O VIII, indicating that the emitting gas is photoionized. The He-like emission appears to be resolved into forbidden and intercombination line components, which implies a high density of >10^{10} cm^{-3}, while the Oxygen lines are velocity broadened with a mean width of ~2600 km s^{-1} (FWHM). The density and widths of the ionized lines indicate an origin of the gas on sub-parsec scales in the Broad Line Region (BLR).The X-ray continuum of 3C 445 is heavily obscured either by a partial coverer or by a photoionized absorber of column density N_{H}=2x10^{23} cm^{-2} and ionization parameter log(xi)=1.4 erg cm s^{-1}. However the view of the X-ray line emission is unobscured, which requires the absorber to be located at radii well within any parsec scale molecular torus. Instead, we suggest that the X-ray absorber in 3C 445 may be associated with an outflowing, but clumpy, accretion disk wind with an observed outflow velocity of ~10000 km/s.