Line Intensity Ratios Research Articles

New Near-infrared Imaging and Spectroscopy of NGC 2071-IR

Abstract We present high-resolution images of NGC 2071-IR in the J, H, and K bands and in the emission at 2.12 μm of the v = 1–0 S(1) line of molecular hydrogen. We also present moderate-resolution K-band spectra of two young stellar objects, IRS 1 and IRS 3, within NGC 2071-IR, that are candidate sources of one or more of the outflows observed in the region. Two of the eight originally identified infrared point sources in NGC 2071-IR are binaries, and we identify two new sources, one coincident with the radio source Very Large Array-1 and highly reddened. The H2 Q(3)/S(1) line intensity ratios at IRS 1 and IRS 3 yield high and very high extinctions, respectively, to them, as is implied by their near-infrared colors and K-band continuum slopes. The spectra also reveal the presence of hot, dense circumstellar molecular gas in each, suggesting that both are strong candidates for having energetic molecular outflows. We agree with a previous suggestion that IRS 1 is the likely source of an east–west-oriented outflow and conclude that this outflow is probably largely out of the plane of the sky. We also conclude that if IRS 3 is the source of the large-scale northeast–southwest outflow, as has been previously suggested, its jet/wind must precess in order to explain the angular width of that outflow. We discuss the nature of the point sources and their possible contributions, if any, to the complex morphology of the H2 line emission.

Spark-induced breakdown spectroscopy for fuel-air equivalence ratio measurements at internal combustion engine-relevant conditions

Spark-induced Breakdown Spectroscopy was used for local fuel-air equivalence ratio measurements of premixed methane-air mixtures by a discharge from an inductive ignition system in a constant volume cell. Elemental emissions of hydrogen Balmer-alpha line (Hα), nitrogen (N746) and oxygen (O777) were experimentally observed in the vicinity of the electrode gap, using a lens-coupled spectrometer and an intensified camera. After optimization of the gating strategy, the spectral emission features, i.e. line intensity ratios and peaks width (full width at half maximum) ratios were analyzed and their relation with the local fuel-air equivalence ratio at the spark plug was discussed, for operating pressures ranging from 10 to 20 bar.Results showed that a change in pressure and temperature did not affect the spectral emissions' atomic peaks ratios, as long as the density was kept constant. For tests at constant temperature and at constant pressure, the peaks intensity ratios showed a linear correlation with local fuel-air equivalence ratio, while peaks width did not show noticeable changes. When pressure was varied, while keeping temperature and fuel-air equivalence ratio constant, a different behavior was observed: peaks intensity ratio were only slightly affected by pressure change, more prominently at fuel-rich conditions, while a peak broadening was clearly recognizable, as the peak width linearly increased with pressure.Moreover, an additional optical setup involving a fiber-optic spark plug was implemented with the aim to adapt the proposed diagnostic tool to engines in operando. Comparisons with the lens setup showed that the developed technique is promising as a compact and versatile tool for applications involving local fuel-air equivalence ratio measurements at different ambient conditions.

Spectroscopic studies on the enhanced radiation with high Z rare gas seeding for mitigating divertor heat loads in LHD plasmas

Abstract We have measured extreme ultraviolet (EUV) and soft X-ray emission spectra of krypton (Kr) ions in the Large Helical Device (LHD) plasmas with Kr gas seeding intended for mitigating divertor heat loads. Several isolated lines or quasi-continuum bands from ion stages in the range of Kr5+–Kr25+ have been identified in a variety of wavelength ranges. The time trends of the line intensities indicate major contributions of ions with M-shell (n = 3) outermost electrons to the enhanced total radiation in the region closer to the core plasma. A line intensity ratio analysis for Kr25+ implies an unignorable contribution of the recombining component for the emissivity from this ion stage. A difference between the trends of neon (Ne) and Kr is also observed in a discharge with a combination of Kr and Ne seedings intended for more effective radiation enhancement.

H2 dissociation in Ar–H2 arc discharge of moderate pressure

The line intensity ratio technique for estimation of hydrogen-to-argon density ratio and hydrogen molecule dissociation degree in arc discharge in Ar–H2 mixtures at moderate pressures (2–3 Torr) is analyzed. Intensity ratios of three hydrogen lines of Balmer series (Hα (656.3 nm), Hβ (486.3 nm) and Hγ (434.0 nm)) to ArI 750.4 nm (2p1 → 1 s2) and ArI 811.5 nm (2p9 → 1s5) lines were examined. Effect of Ar fraction in Ar–H2 mixtures on the diagnostic technique and molecular hydrogen dissociation degree in the large-volume high-density moderate-pressure Ar–H2 arc was studied. Using ArI 811 nm line for the intensity ratio diagnostics in the arc discharge is not valid due to great role of the excitation from 1s5 in production of Ar 2p9 level. It is shown that to obtain the correct H density value it is necessary to account quenching of H* excited states by Ar atoms and H2 molecules. Pair of Hα and ArI 750 nm lines is the best choice for determining atomic hydrogen density using HI-to-ArI line intensity ratio technique because of the upper excited state of Hα (n = 3) is less subjected to quenching by Ar atoms and H2 molecules as compared with higher H* levels (n = 4, 5). It is shown increasing Ar fraction in Ar–H2 mixtures results in growth of the molecular hydrogen dissociation degree.

Determination of hafnium in zirconium materials

An arc atomic emission technique of hafnium determination in zirconium is developed and tested. The study was carried out on a PGS-2 spectrometer equipped with MAÉS analyzer and information processing software «Atom 3.3». («VMK-Optoélektronika», Novosibirsk). Excitation of spectra of pre-oxidized metal was carried out using a medium-frequency generator «Vesuvius» («VMK-Optoélektronika», Novosibirsk). Analytical line of hafnium was free of spectral overlap with the lines of zirconium. We have set a current of the AC arc discharge (20 A), exposure time (30 sec) and the form of the electrode into which the sample is placed («narrow crater») are selected. The effect of buffering additives (graphite powder, bismuth fluoride) on the intensity of the analyte lines was studied. It is shown that high sensitivity of the analyte is observed for oxidized material without additives. Reduction of the random error attributed to the influence of conditions of spectrum excitation and sample preparation is achieved using the intensity ratio of the analyte line and zirconium as an analytical signal. Recommendations regarding preparation of the samples for calibration are given. The lower limit of the determined concentration is 0.01% with a relative standard deviation in repeatability 3%.

Population modelling of the He II energy levels in tokamak plasmas: I. Collisional excitation model

Helium is widely used as a fuel or minority gas in laboratory fusion experiments, and will be present as ash in DT thermonuclear plasmas. It is therefore essential to have a good understanding of its atomic physics. To this end He II population modelling has been undertaken for the spectroscopic levels arising from shells with principal quantum number n = 1–5. This paper focuses on a collisional excitation model; ionisation and recombination will be considered in a subsequent article. Heavy particle collisional excitation rate coefficients have been generated to supplement the currently-available atomic data for He II, and are presented for proton, deuteron, triton and α-particle projectiles. The widely-used criterion for levels within an n shell being populated in proportion to their statistical weights is reassessed with the most recent atomic data, and found not to apply to the He II levels at tokamak densities (1018–1021 m−3). Consequences of this and other likely sources of errors are quantified, as is the effect of differing electron and ion temperatures. Line intensity ratios, including the so-called ‘branching ratios’ and the fine-structure β1, β2, β3 and γ ratios, are discussed, the latter with regard to their possible use as diagnostics.

Surface Hardness Analysis of Aged Composite Insulators via Laser-Induced Plasma Spectra Characterization

Silicone rubber composite materials, especially high-temperature vulcanized (HTV) insulators, are widely used in high-voltage transmission lines. Previous studies have shown that the degree of aging of an HTV material is approximately linear with its hardness. The hardness measurement relies on laboratory analysis after sampling, and there is no alternative hardness test available for on-site application. In this paper, the ablation characteristics of HTV materials and the spectral and temperature characteristics of the corresponding plasmas were investigated via laser-induced breakdown spectroscopy (LIBS), thereby laying the foundation for the subsequent use of LIBS technology for on-site hardness characterization. A linear relationship was found between the hardness (either macroscopic or microscopic) of an HTV material and the intensity ratio of the ion line to the atomic line in the spectral data as well as a linear relationship between the hardness and the average plasma temperature corresponding to the aging layer. The results show that LIBS can serve as an effective source of hardness information for an HTV material and is therefore helpful for maintaining the safety of transmission lines.

Consistency of intensity ratio between spectral lines with similar self-absorption characteristics during ungated laser induced breakdown spectroscopy measurements

This work reports that the intensity ratio of spectral lines having similar self-absorption characteristics during laser induced breakdown spectroscopy (LIBS) analysis can become nearly constant over a wide range of irradiation conditions if the intensities are integrated over a sufficiently long time. It is shown that the plasma temperature and intensity ratio of these spectral lines have temporal similarity. The spectral lines with similar self-absorption properties may be selected to improve the accuracy and consistency of LIBS analysis results under an environment with fluctuating measurement conditions.

Effect of lens focusing distance on laser-induced silicon plasmas at different sample temperatures

We investigated the dependence of laser-induced breakdown spectral intensity on the focusing position of a lens at different sample temperatures (room temperature to 300 °C) in atmosphere. A Q-switched Nd:YAG nanosecond pulsed laser with 1064 nm wavelength and 10 ns pulse width was used to ablate silicon to produce plasma. It was confirmed that the increase in the sample’s initial temperature could improve spectral line intensity. In addition, when the distance from the target surface to the focal point increased, the intensity firstly rose, and then dropped. The trend of change with distance was more obvious at higher sample temperatures. By observing the distribution of the normalized ratio of Si atomic spectral line intensity and Si ionic spectral line intensity as functions of distance and temperature, the maximum value of normalized ratio appeared at the longer distance as the initial temperature was higher, while the maximum ratio appeared at the shorter distance as the sample temperature was lower.

Using Xps Data for Determining Spatial Distribution of Metals in Bimetallic Particles Supported on a Flat Surface

Expressions are obtained for the intensities of photoemission lines of silver and gold in bimetallic particles formed during sequential deposition of metals on the flat surface of the support. Two cases are considered: bimetallic particles with a non-uniform distribution of metals (silver core covered with a gold shell) and alloy particles of uniform composition. The particle shapes are assumed to be hemispherical. Expressions were obtained for the photoemission lines of gold Au4f, Au3d3/2 and silver Ag3d as well as for the Auger line of silver AgMVV recorded using radiation AlKα (hν = 1486.6 eV) and AgLα (hν = 2983.4 eV). Gold shells on the surface of silver particles are shown to diminish the intensity ratio of AgMVV line to Ag3d line, and this effect becomes stronger with the increasing ratio γ of gold atoms to silver atoms. In the case of alloy particles Ag–Au, the intensity ratio of these lines also decreases with increasing γ, though to a much lesser extent. The intensity ratios of gold Au4f and Au3d3/2 lines to the silver Ag3d line are also considered. The obtained equations can be used in XPS studies to consider formation of bimetallic particles in model planar systems and the changes occurring with the particles as a result of heat treatment in a vacuum or in a reaction medium.

Investigation on the dynamic characteristics of LIBS for heavy metal Mn in liquid matrix

Laser-induced breakdown spectroscopy in composition analysis of materials has many advantages over other analytical methods.Based on our Laser Induced Breakdown Spectroscopy (LIBS) survey system of heavy metals in the mixed solution and the optimum experimental parameters, we measured the integrated intensities of partial spectral lines of Mn when the ICCD gate delay time and the sample flow rate were ranged from 500ns to 2500ns, 35ml/min to 55ml/min respectively. With increasing the time delay, the electron temperature of the plasma decreases gradually, the electron density decreases firstly,then the change amplitude tends to be flat.As the flow rate continue increasing,the electron temperature of plasma increases firstly, then the change tends to be flat, the electron density increase gradually.The element particle density ratio of Mn at first ionization state to ground state and Mn at first ionization state are also obtained respectively. Finally, by comparing the experimental value of spectral line intensity ratio of Mn with the calculated value, the nonexistent conditions of local thermal equilibrium and self-absorption of laser plasma are verified.It provides the suppuration for forward quantitative analysis of the trace heavy metal elements in liquid matrix.

Temporal-spatial resolved laser-induced breakdown spectroscopy of T91 steel of different aging grades

As a representative heatproof martensitic steel, T91 steel is extensively used for building industrial pressure-bearing heat-exchange surface. The mechanical properties and metallographic structure of the steel components will gradually change in long-term operation (also known as material aging). It will seriously endanger the operation safety and reduce the lifespan of the equipment. In this study, in order to deeply understand the mechanism of steel degradation surface measurement by laser-induced breakdown spectroscopy (LIBS), the temporal-spatial evolutions of spectral line emissions of T91 steel specimens with different aging grades were observed by using grating spectrometer with intensified charge coupled device detector (ICCD). The time-resolved line intensity ratios of ionic to atomic and matrix element to alloying element of specimens with different aging grade were investigated. Besides, the time-resolved plasma temperatures of different specimens were studied. And the three-dimensional surface topographies of ablated craters of specimens with different aging grades were analyzed. The study results show that the line emissions are located at greater height above surface for the specimen with lower steel aging grade during the early stage of the plasma expansion (300–700 ns delay time). The integrated line intensities which are close to the specimen surface (at≈0–500 μm above specimen surface) increase with the increase of steel aging grade during 300–700 ns delay time. The line intensity ratios are correlated with the steel aging grade at specific height above specimen surface during 500–700 ns delay time, and these correlations are sensitive to the delay time and observation distance from specimen surface. In addition, it was found that the plasma temperatures of specimens with lower aging grades are higher during 300–700 ns delay time. And the depth and volume of ablated crater increase with the increase of the steel aging grade. The investigations create a better understanding of physical mechanism in LIBS steel degradation analysis, and provide a good reference for practical measurement.

Spectroscopic study of EUV and SXR transitions of Cu XIX with plasma parameters

Extensive and elaborate theoretical computations of Cu XIX have been performed by employing multi-configuration Dirac-Fock (MCDF) method. We have presented energy levels and radiative data such as, transition wavelengths, radiative rates, oscillator strengths and line strengths for electric dipole (E1) transitions in Na-like Cu. For other types of transitions, namely magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2), only the A-values are listed. We have also discussed the importance and the effect of valence-valence (VV) and core-valence (CV) correlations on the excitation energies in graphical as well as in tabular form. The accuracies of the presented levels, wavelengths, transition rates and lifetimes are assessed by comparing them to available experimental and other theoretical results. Analogous calculations have been carried out by using Flexible Atomic Code (FAC) based on self-consistent Dirac-Fock-Slater iteration method. QED corrections due to vacuum polarization and self-energy effects, and Breit correction due to the exchange of virtual photons between two electrons are fully considered and their effects on the energy levels are studied graphically. The fine-structure energy levels have also been reported by using the Configuration Interaction (CIV3) technique. An intercomparison among three independent calculations helps us in assessing the credibility and integrity of our reported data. Additionally, we have shown the variation of the line intensity ratios and electron density with plasma temperature graphically for Cu XIX. We have also identified Extreme Ultraviolet (EUV) and Soft X-ray (SXR) transitions and believe that our reported results may be beneficial in space and laboratory plasma research.

Optical diagnostics of helium recombining plasmas with collisional radiative model

Optical diagnostics for plasmas has many advantages that allow for the determination and understanding of plasma parameters. A method employing the line intensity ratio (LIR), combined with the collisional-radiative (CR) model considering the radiation trapping effect (RTE), was developed to analyze the recombining helium plasmas. The recombining plasma component and the ionizing plasma components in the He CR-model were evaluated, and the RTEs for from the ground state to n1P states were analyzed. The electron temperature and density of the helium recombining plasmas were determined using seven LIRs with the He CR-model, considering the RTEs of 11S–31P, 11S–41P, and 11S–51P. When the He gas pressure was above 100 mTorr, the electron temperature was less than 0.8 eV and the electron density was more than 1012 cm−3. The determined plasma parameters were compared with those obtained by the continuum method and in reasonable agreement with those by the continuum method.

Shielding of the azimuthal magnetic field by the anode plasma in a relativistic self-magnetic-pinch diode

In relativistic electron beam diodes, the self-generated magnetic field causes electron-beam focusing at the center of the anode. Generally, plasma is formed all over the anode surface during and after the process of the beam focusing. In this work, we use visible-light Zeeman-effect spectroscopy for the determination of the magnetic field in the anode plasma in the Sandia 10 MV, 200 kA (RITS-6) electron beam diode. The magnetic field is determined from the Zeeman-dominated shapes of the Al III 4s–4p and C IV 3s–3p doublet emissions from various radial positions. Near the anode surface, due to the high plasma density, the spectral line-shapes are Stark-dominated, and only an upper limit of the magnetic field can be determined. The line-shape analysis also yields the plasma density. The data yield quantitatively the magnetic-field shielding in the plasma. The magnetic-field distribution in the plasma is compared to the field-diffusion prediction and found to be consistent with the Spitzer resistivity, estimated using the electron temperature and charge-state distribution determined from line intensity ratios.

Characterization Of Human Teeth By Laser-Induced Breakdown Spectroscopy

We present in this report the results of characterization of human teeth by Laser-Induced Breakdown Spectroscopy, LIBS (100 mJ, 7 ns, 1064 nm) in surrounding He gas of 55 mL/s. Measurements were carried out on human teeth on dentine and enamel (apical and buccal) until about of 45 μm depth from surface. The results showed that the Indonesian human teeth contain some elements such as Ca, F, Si, Zn, Na, Sn, Ar, Li, K, Ce, Fe, Mn, Ti, Al, Cr and P. In addition, based on line intensity ratio of ionic Ca II (396.84 nm) to neutral Ca I (422.67 nm), the apical enamel part is the hardest of all.

Detection of 84 GHz Class I Methanol Maser Emission toward NGC 253

Abstract We have investigated the central region of NGC 253 for the presence of 84.5 GHz (5−1 → 40E) methanol emission using the Australia Telescope Compact Array. We present the second detection of 84.5 GHz class I methanol maser emission outside of the Milky Way. This maser emission is offset from the dynamical center of NGC 253, in a region with previously detected emission from class I maser transitions (36.2 GHz 4−1 → 30E and 44.1 GHz 70 → 61A+ methanol lines). The emission features a narrow linewidth (∼12 ) with a luminosity approximately that is 5 orders of magnitude higher than typical Galactic sources. We determine an integrated line intensity ratio of 1.2 ± 0.4 between the 36.2 and 84.5 GHz class I methanol maser emission, which is similar to the ratio observed toward Galactic sources. The three methanol maser transitions observed toward NGC 253 each show a different distribution, suggesting differing physical conditions between the maser sites, and also that observations of additional class I methanol transitions will facilitate investigations of the maser pumping regime.

Design of tangential x-ray crystal spectrometer for Aditya-U tokamak.

A tangential soft x-ray crystal spectrometer has been designed to measure the x-ray spectrum of He-like argon for the Aditya-U tokamak plasma. The system enables to measure electron temperature using the intensity ratio of the resonance line to the satellite line. For this purpose, an x-ray spectral line at 3.9494 Å from He-like argon, Ar16+, is considered. The spectrometer consists of a cylindrically bent silicon (111) crystal and a CCD detector to measure the resonance spectral line and its satellite lines in the wavelength region of 3.94-4.0 Å, viewing the plasma tangentially at an angle of 26° with respect to the toroidal direction in the magnetic axis. Considering Aditya-U tokamak plasma parameters and its geometrical constraints, plasma to crystal and crystal to detector distances have been kept at 1.47 m and 0.5 m, respectively, to detect a sufficient signal. The engineering design has been optimized after adequately addressing the issues related to port geometry and machine accessibility. Details on the design of the crystal spectrometer are presented in this paper.

Comparing the emission spectra of U and Th hollow cathode lamps and a new U line list

Context. Thorium hollow cathode lamps (HCLs) are used as frequency calibrators for many high resolution astronomical spectrographs, some of which aim for Doppler precision at the 1 m s−1 level. Aims. We aim to determine the most suitable combination of elements (Th or U, Ar or Ne) for wavelength calibration of astronomical spectrographs, to characterize differences between similar HCLs, and to provide a new U line list. Methods. We record high resolution spectra of different HCLs using a Fourier transform spectrograph: (i) U–Ne, U–Ar, Th–Ne, and Th–Ar lamps in the spectral range from 500 to 1000 nm and U–Ne and U–Ar from 1000 to 1700 nm; (ii) we systematically compare the number of emission lines and the line intensity ratio for a set of 12 U–Ne HCLs; and (iii) we record a master spectrum of U–Ne to create a new U line list. Results. Uranium lamps show more lines suitable for calibration than Th lamps from 500 to 1000 nm. The filling gas of the lamps significantly affects their performance because Ar and Ne lines contaminate different spectral regions. We find differences (up to 88%) in the line intensity of U lines in different lamps from the same batch. We find 8239 isolated lines between 500 and 1700 nm that we attribute to U, 3379 of which were not contained in earlier line lists. Conclusions. We suggest using a combination of U–Ne and U–Ar lamps to wavelength-calibrate astronomical spectrographs up to 1 μm. From 1 to 1.7 μm, U–Ne shows better properties. The differences in line strength between different HCLs underline the importance of characterizing HCLs in the laboratory. The new 3379 U lines can significantly improve the radial velocity precision of astronomical spectrographs.

Structural parameters and cation distributions in solid state synthesized Ni-Zn ferrites

A series of Nickel-Zinc ferrite samples were synthesized by low-energy ball milling with subsequent thermal treatment in air at 1200 °C for 12 h. X-ray Diffraction patterns confirm the formation of the ferrite phases. Lattice parameters were found to increase almost linearly from 8.3366 Å to 8.4387 Å with the increment of zinc substitution. The oxygen parameters also increased and were found to closely follow an earlier proposed power law equation. The cation-oxygen bond lengths, suggest a gradual tetrahedral expansion and octahedral contraction with increasing Zn content. Additionally, the occupation of Zn2+ and Ni2+ ions in all samples has been determined by using the line intensity ratios of diffraction peaks together with a proposed general chemical formula. From the calculated cation distributions, it was found that the theoretical lattice parameters agree with the experimental ones. By using, the Williamson-Hall method, an average crystallite size of ∼36 nm was found.