Emission Line Intensity Ratios Research Articles

Emission Line Intensity Ratios of Fe xxvi/ xxv/ xxiv in Solar Flares Observed by Hinotori

High-resolution spectra observed by the Solar X-ray spectrometer on board the Hinotori mission are revisited. Flat crystals slightly offset to the satellite spin axis produce automatic spectral scans for emission lines emerging from highly charged iron ions in solar flares every half-spin time period. All the downlinked data of the mission are converted to FITS format and major flare spectral data are revived as IDL save files in ISAS/DARTS. Based on these data sets, single-temperature fits are performed for the emission line complex of highly charged iron ions in the wavelength range of 1.75–1.95 Å and compared with theoretical predictions. Synthetic spectra with single electron temperatures estimated from j/w line-intensity ratios fit fairly well for Fe xxiv and Fe xxiii lines in the wavelength range of 1.85–1.88 Å, while intensity ratios of Fe xxv lines (x, y, z) and the inner-shell excitation line of Fe xxiv (q) to the Fe xxv resonance line (w) have systematic excesses. Empirical relations for the observed line ratios are derived. Ion fractions of Fe+25/Fe+24 estimated by intensity ratios of Lyα/w in the temperature range of log T e =7.25–7.45 are consistent with values in ionization equilibrium, and the remaining excesses of the Fe xxv line ratios may suggest problems with the atomic parameters or atomic modeling.

HOPS 361-C’s Jet Decelerating and Precessing through NGC 2071 IR

We present a two-epoch Hubble Space Telescope study of NGC 2071 IR highlighting HOPS 361-C, a protostar producing an arced 0.2 parsec-scale jet. The proper motions for the brightest knots decrease from 350 to 100 km s−1 with increasing distance from the source. The [Fe ii] and Paβ emission line intensity ratio gives a velocity jump through each knot of 40–50 km s−1. A new [O i] 63 μm spectrum, taken with the German REciever for Astronomy at Terahertz frequencies instrument aboard Stratospheric Observatory for Infrared Astronomy, shows a low line-of-sight velocity indicative of high jet inclination. Proper motions and jump velocities then estimate 3D flow speed for knots. Subsequently, we model knot positions and speeds with a precessing jet that decelerates. The measurements are matched with a precession period of 1000–3000 yr and half opening angle of 15°. The [Fe ii] 1.26-to-1.64 μm line intensity ratio determines visual extinction to each knot from 5 to 30 mag. Relative to ∼14 mag of extinction through the cloud from C18O emission maps, the jet is embedded at a 1/5–4/5 fractional cloud depth. Our model suggests the jet is dissipated over a 0.2 pc arc. This short distance may result from the jet sweeping through a wide angle, allowing the cloud time to fill cavities opened by the jet. Precessing jets contrast with nearly unidirectional protostellar jets that puncture host clouds and can propagate significantly farther.

Analysis of line intensity ratio for optical transitions of 3d6 levels and plasma screening effect on atomic structure of Fe III ion

Iron emission lines are observed from most classes of astronomical objects through a wide spectral range from infrared to X-ray. For a useful analysis of these lines, accurate atomic data for neutral iron and its ions is required. In this work, we have done calculations of energy levels and radiative data of Fe III by using the relativistic configuration interaction method with the implementation of the flexible atomic code (FAC). We have calculated emission-line intensity ratios for optical transitions among the fine-structure levels of the 3d6 configuration at temperature 104 K and density ne=104cm−3. We have also compared our results with the observed spectra of Herbig-Haro objects HH 202 of Orion Nebula, Planetary Nebula, and NGC 2392, post-asymptotic giant branch star (PAGB) HD341617. We have also discussed various discrepancies between the observed spectra from these nebulae and our calculations. The atomic structure of plasma-embedded Fe III is also analyzed using flexible atomic code (FAC). The graphical study shows that transition wavelengths, oscillator strengths, and transition rates are very sensitive to the plasma environment in the density range 1021cm−3 to 5×1022cm−3 and spectral lines associated to Δn = 0 transitions for Fe III ion are blueshifted. We have also studied the dependence of emission line intensity ratios on plasma density and temperature. We believe that our presented results are useful in spectroscopic analysis and examination of astrophysical and laboratory plasma.

Dual functionality luminescence thermometry with Gd2O2S:Eu3+,Nd3+ and its multiple applications in biosensing and in situ temperature measurements

Luminescence thermometry using sharp line emission of lanthanide ions has become an active area of research as it offers the advantages of remote temperature sensing with high sensitivity and superior spatial resolution. The most widely applied method relies on the temperature dependence of the luminescence intensity ratio of emission lines from two thermally coupled levels. However, the usable temperature range for this type of Boltzmann thermometer is limited. In addition, the weak and narrow line absorption of the parity forbidden 4f-4f transitions of lanthanides forms a serious drawback. To solve both problems, we here report a new dual functionality luminescence thermometer: Gd2O2S co-doped with Eu3+ and Nd3+. This material combines Boltzmann and energy transfer thermometry to extend the temperature range and uses the strong and broad charge transfer absorption band of Eu3+ for sensitization. In the T-range of 300–500 K efficient energy transfer from Eu3+ to Nd3+ allows for charge transfer-sensitized luminescence thermometry using near infrared emission from the thermally coupled 4F3/2 and 4F5/2 levels of Nd3+. Above 500 K a high temperature sensitivity is obtained using the strong temperature dependence of the luminescence intensity ratio of red Eu3+ to near infrared Nd3+ emission. The dual-functionality provides a single thermometer combining strong absorption and high relative sensitivity (0.6 – 1.4%) over a wide temperature range (300 to 650 K). Finally, it is proposed that this dual-function luminescent thermometer has promising potential for multifunctional applications in biosensors and in situ temperature measurements of chemical reaction process.

Chemical abundance of LINER galaxies – metallicity calibrations based on SDSS-IV MaNGA

ABSTRACT The ionizing source of low-ionization nuclear emission-line regions (LINERs) is uncertain. Because of this, an empirical relation to determine the chemical abundances of these objects has not been proposed. In this work, for the first time, we derived two semi-empirical calibrations based on photoionization models to estimate the oxygen abundance of LINERS as a function of the N2 and O3N2 emission-line intensity ratios. These relations were calibrated using oxygen abundance estimations obtained by comparing the observational emission-line ratios of 43 LINER galaxies (taken from the MaNGA survey) and grids of photoionization models built with the cloudy code assuming post-asymptotic giant branch stars with different temperatures. We found that the oxygen abundance of LINERs in our sample is in the $\rm 8.48 \: \lesssim \: 12+log(O/H) \: \lesssim 8.84$ range, with a mean value of $\rm 12+\log (O/H)=8.65$. We recommend the use of the N2 index to estimate the oxygen abundances of LINERs, since the calibration with this index presented a much smaller dispersion than the O3N2 index. In addition, the estimated metallicities are in good agreement with those derived by extrapolating the disc oxygen abundance gradients to the centre of the galaxies showing that the assumptions of the models are suitable for LINERs. We also obtained a calibration between the logarithm of the ionization parameter and the [O iii]/[O ii] emission-line ratio.

Insights from Collisional-Radiative Models of Neutral and Singly Ionized Xenon in Hall Thrusters

Collisional-radiative (CR) models for neutral and singly ionized xenon have been constructed for applications to Hall thruster diagnostics. The models use primarily theoretical electron-impact excitation cross sections calculated using the Dirac B-spline R-matrix method. This paper describes the models’ construction and their validation against heritage CR models and previously published Hall thruster data, and then outlines several applications. The baseline 0D steady-state models are used to investigate electron density dependence in neutral xenon emission line intensity ratios commonly used to measure electron temperature, and also to demonstrate that stepwise ionization through excited states is an important process in Hall thrusters. The models are extended to evaluate impacts of neutral and ion transport on 0D CR model applicability, intrinsic bandwidth limits for time-dependent line intensity measurements, and errors introduced when the plasma is assumed to be optically thin.

A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Abstract. With the recurring interest in rare earth elements (REEs), laser-induced fluorescence (LiF) may provide a powerful tool for their rapid and accurate identification at different stages along their value chain. Applications to natural materials such as minerals and rocks could complement the spectroscopy-based toolkit for innovative, non-invasive exploration technologies. However, the diagnostic assignment of detected emission lines to individual REEs remains challenging because of the complex composition of natural rocks in which they can be found. The resulting mixed spectra and the large amount of data generated demand automated approaches of data evaluation, especially in mapping applications such as drill core scanning. LiF reference data provide the solution for robust REE identification, yet they usually remain in the form of tables of published emission lines. We show that a complete reference spectra library could open manifold options for innovative automated analysis. We present a library of high-resolution LiF reference spectra using the Smithsonian rare earth phosphate standards for electron microprobe analysis. We employ three standard laser wavelengths (325, 442, 532 nm) to record representative spectra in the UV-visible to near-infrared spectral range (340–1080 nm). Excitation at all three laser wavelengths yielded characteristic spectra with distinct REE-related emission lines for EuPO4, TbPO4, DyPO4 and YbPO4. In the other samples, the high-energy excitation at 325 nm caused unspecific, broad-band defect emissions. Here, lower-energy laser excitation is shown to be successful for suppressing non-REE-related emission. At 442 nm excitation, REE reference spectra depict the diagnostic emission lines of PrPO4, SmPO4 and ErPO4. For NdPO4 and HoPO4 the most efficient excitation was achieved with 532 nm. Our results emphasise the possibility of selective REE excitation by changing the excitation wavelength according to the suitable conditions for individual REEs. Our reference spectra provide a database for the transparent and reproducible evaluation of REE-bearing rocks. The LiF spectral library is available at zenodo.org and the registered DOI https://doi.org/10.5281/zenodo.4054606 (Fuchs et al., 2020). Primarily addressing the raw material exploration sector, it aids particularly the development of advanced data processing routines for LiF analysis but can also support further research on the REE luminescence in natural rocks or artificial compounds. It gives access to traceable data for the comparison of emission line positions, emission line intensity ratios and splitting into emission line sub-levels or can be used as reference or training data for automated approaches of component assignment.

Chemical abundances in Seyfert galaxies – VI. Empirical abundance calibration

ABSTRACT We derived a bi-dimensional calibration between the emission-line ratios $R_{23}= ([\mathrm{ O}\, {\small {\rm II}}]\,\lambda 3726 +\lambda 3729 +[\mathrm{ O}\mathrm{ }\, {\small {\rm III}}]\,\lambda 4959 + \lambda 5007)/\rm H\,\beta$, ${\it P}=[([\mathrm{ O}\, {\small {\rm III}}]\,\lambda 4959+\lambda 5007)/{\rm H}\,\beta ]/R_{23}$ and the oxygen abundance relative to hydrogen (O/H) in the gas phase of Seyfert 1 and 2 nuclei. In view of this, emission-line intensity ratios for a sample of objects taken from the Sloan Digital Sky Survey Data Release 7 measured by the MPA/JHU group and direct estimates of O/H based on Te-method, adapted for active galactic nuclei (AGNs), are considered. We find no variation of R23 observed along the radii of AGNs, which shows that this line ratio is a good oxygen abundance (O/H) indicator for the class of objects considered in this work. The derived O/H = f(R23, P) relation produces O/H values similar to estimations via Te-method in a wide range of metallicities [$\rm 8.0 \: \lesssim \: 12+\log \,(O/H) \: \lesssim \: 9.2$]. Conversely to star-forming regions in the high-metallicity regime, R23 shows a positive correlation trend with O/H in AGNs. This indicates that the hardness of ionizing radiation is not affected by the metallicities in these objects or narrow-line regions are not significantly modified by changes in the spectral energy distribution due to metallicity variations.

Raining in MKW 3 s: A Chandra-MUSE Analysis of X-Ray Cold Filaments around 3CR 318.1

Abstract We present the analysis of X-ray and optical observations of gas filaments observed in the radio source 3CR 318.1, associated with NGC 5920, the brightest cluster galaxy (BCG) of MKW 3 s, a nearby cool core galaxy cluster. This work is one of the first X-ray and optical analyses of filaments in cool core clusters carried out using MUSE observations. We aim at identifying the main excitation processes responsible for the emission arising from these filaments. We complemented the optical VLT/MUSE observations, tracing the colder gas phase, with X-ray Chandra observations of the hotter highly ionized gas phase. Using the MUSE observations, we studied the emission line intensity ratios along the filaments to constrain the physical processes driving the excitation, and, using the Chandra observations, we carried out a spectral analysis of the gas along these filaments. We found a spatial association between the X-ray and optical morphology of these filaments, which are colder and have lower metal abundance than the surrounding intracluster medium (ICM), as already seen in other BCGs. Comparing with previous results from the literature for other BCGs, we propose that the excitation process that is most likely responsible for these filaments emission is a combination of star formation and shocks, with a likely contribution from self-ionizing, cooling ICM. Additionally, we conclude that the filaments most likely originated from AGN-driven outflows in the direction of the radio jet.

Emission spectroscopic study of an analytical glow discharge with plane and hollow cathodes: Titanium and iron in argon discharge

An extensive analysis of Ti and Fe emission spectra from both plane and hollow cathode glow discharges in argon in Grimm-type geometry, measured by high resolution Fourier transform spectrometer has allowed a novel comparison of excitation mechanisms. Deviations from simple models of laboratory plasmas assuming local thermodynamic equilibrium are observed. Analyte ionization in both discharge modes is dominated by charge transfer (CT) between Ar+ ions and neutral analyte atoms, while this process is more pronounced in a plane cathode than hollow cathode discharge. Radiative decay of the CT-excited levels is found to cause overpopulation of long-lived ground term and metastable analyte ions, relative to the equilibrium number densities that would be expected from the Saha-Boltzmann distribution. This overpopulation is found to spread into high-energy levels of neutral atoms by collisional 3-body recombination with electrons. Lower atomic levels of the analytes are excited by collisions with electrons, the number density of which is not high enough to support conditions close to local thermodynamic equilibrium. The analysis of the spectra is based on experimental Boltzmann plots, transition rate diagrams and intensity ratios of emission lines measured in both discharge configurations. Uncertainty propagation in the data processing procedures is analyzed and described.

Improved Fe ii Emission-line Models for AGNs Using New Atomic Data Sets

Abstract Understanding the Fe II emission from active galactic nuclei (AGNs) has been a grand challenge for many decades. The rewards from understanding the AGN spectra would be immense, involving both quasar classification schemes such as “Eigenvector 1” and tracing the chemical evolution of the cosmos. Recently, three large Fe II atomic data sets with radiative and electron collisional rates have become available. We have incorporated these into the spectral synthesis code Cloudy and examined predictions using a new generation of AGN spectral energy distribution (SED), which indicates that the ultraviolet (UV) emission can be quite different depending on the data set utilized. The Smyth et al. data set better reproduces the observed Fe II template of the I ZW 1 Seyfert galaxy in the UV and optical regions, and we adopt these data. We consider both thermal and microturbulent clouds and show that a microturbulence of ≈100 km s−1 reproduces the observed shape and strength of the so-called Fe II “UV bump.” Comparing our predictions to the observed Fe II template, we derive a typical cloud density of 1011 cm−3 and photon flux of 1020 cm−2 s−1, and show that these largely reproduce the observed Fe II emission in the UV and optical. We calculate the I(Fe II)/I(Mg II) emission-line intensity ratio using our best-fitting model and obtain log(I(Fe II)/I(Mg II)) ∼ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance ratio. Finally, we vary the Eddington ratio and SED shape as a step in understanding the Eigenvector 1 correlation.

Enhancing composition control of alloy nanoparticles from gas aggregation source by in operando optical emission spectroscopy

AbstractThe use of multicomponent targets allows the gas‐phase synthesis of a large variety of alloy nanoparticles (NPs) via gas aggregation sources. However, the redeposition of sputtered material impacts the composition of alloy NPs, as demonstrated here for the case of AgAu alloy NPs. To enable NPs with tailored Au fractions, in operando control over the composition of the NPs is in high demand. We suggest the use of optical emission spectroscopy as a versatile diagnostic tool to determine and control the composition of the NPs. A strong correlation between operating pressure, intensity ratio of Ag and Au emission lines, and the obtained NP compositions is observed. This allows precise in operando control of alloy NP composition obtained from multicomponent targets.

Multimodal Non-Contact Luminescence Thermometry with Cr-Doped Oxides.

Luminescence methods for non-contact temperature monitoring have evolved through improvements of hardware and sensor materials. Future advances in this field rely on the development of multimodal sensing capabilities of temperature probes and extend the temperature range across which they operate. The family of Cr-doped oxides appears particularly promising and we review their luminescence characteristics in light of their application in non-contact measurements of temperature over the 5–300 K range. Multimodal sensing utilizes the intensity ratio of emission lines, their wavelength shift, and the scintillation decay time constant. We carried out systematic studies of the temperature-induced changes in the luminescence of the Cr3+-doped oxides Al2O3, Ga2O3, Y3Al5O12, and YAlO3. The mechanism responsible for the temperature-dependent luminescence characteristic is discussed in terms of relevant models. It is shown that the thermally-induced processes of particle exchange, governing the dynamics of Cr3+ ion excited state populations, require low activation energy. This then translates into tangible changes of a luminescence parameter with temperature. We compare different schemes of temperature sensing and demonstrate that Ga2O3-Cr is a promising material for non-contact measurements at cryogenic temperatures. A temperature resolution better than ±1 K can be achieved by monitoring the luminescence intensity ratio (40–140 K) and decay time constant (80–300 K range).

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

ABSTRACT We have modelled the stellar and nebular continua and emission-line intensity ratios of massive stellar populations in the Antennae galaxy using high resolution and self-consistent libraries of model H ii regions around central clusters of ageing stars. The model libraries are constructed using the stellar population synthesis code, starburst99, and photoionization model, and cloudy. The Geneva and PARSEC stellar evolutionary models are plugged into starburst99 to allow comparison between the two models. Using a spectrum-fitting methodology that allows the spectral features in the stellar and nebular continua [e.g. Wolf–Rayet (WR) features, Paschen jump], and emission-line diagnostics to constrain the models, we apply the libraries to the high-resolution Multi-Unit Spectroscopic Explorer spectra of the starbursting regions in the Antennae galaxy. Through this approach, we were able to model the continuum emission from WR stars and extract stellar and gas metallicities, ages, electron temperatures, and densities of starbursts by exploiting the full spectrum. From the application to the Antennae galaxy, we find that (1) the starbursts in the Antennae galaxy are characterized by stellar and gas metallicities of around solar, (2) the star-forming gas in starbursts in the Western loop of NGC 4038 appears to be more enriched, albeit slightly, than the rest of galaxy, (3) the youngest starbursts are found across the overlap region and over parts of the western-loop, though in comparison, the regions in the western-loop appear to be at a slightly later stage in star formation than the overlap region, and (4) the results obtained from fitting the Geneva and Parsec models are largely consistent.

Chemical abundances of Seyfert 2 AGNs – II. N2 metallicity calibration based on SDSS

ABSTRACT We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic nuclei and the N2 = log([N ii]λ6584/H α) emission-line intensity ratio. This calibration was derived through the [O iii]λ5007/[O ii]λ3727 versus N2 diagram containing observational data and photoionization model results obtained with the cloudy code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift $z \: \lesssim 0.4$) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z–N2 relation is valid for the range $0.3 \: \lesssim \: (Z/{\rm Z}_{\odot }) \: \lesssim \: 2.0$ that corresponds to $-0.7 \: \lesssim \: ({\rm N}2) \: \lesssim \: 0.6$. The effects of varying the ionization parameter (U), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N2. This result indicates the large reliability of our Z –N2 calibration. A relation between U and the [O iii]/[O ii] line ratio, almost independent of other nebular parameter, was obtained.

Quantitative Analysis of Cerium-Gallium Alloys Using a Hand-Held Laser Induced Breakdown Spectroscopy Device

A hand-held laser-induced breakdown spectroscopy device was used to acquire spectral emission data from laser-induced plasmas created on the surface of cerium-gallium alloy samples with Ga concentrations ranging from 0–3 weight percent. Ionic and neutral emission lines of the two constituent elements were then extracted and used to generate calibration curves relating the emission line intensity ratios to the gallium concentration of the alloy. The Ga I 287.4-nm emission line was determined to be superior for the purposes of Ga detection and concentration determination. A limit of detection below 0.25% was achieved using a multivariate regression model of the Ga I 287.4-nm line ratio versus two separate Ce II emission lines. This LOD is considered a conservative estimation of the technique’s capability given the type of the calibration samples available and the low power (5 mJ per 1-ns pulse) and resolving power ( λ / Δ λ = 4000) of this hand-held device. Nonetheless, the utility of the technique is demonstrated via a detailed mapping analysis of the surface Ga distribution of a Ce-Ga sample, which reveals significant heterogeneity resulting from the sample production process.

Statistics of excitonic energy states based on phononic-excitonic-radiative model

Excitation and deexcitation dynamics of excitons in GaN are analyzed by theoretical simulation using a set of rate equations based on a phononic-excitonic-radiative (PXR) model, which is applied to the analysis of experimentally-observed photoluminescence (PL) properties using a short pulse excitation. In phononic processes, deformation and piezoelectric interactions of the LA phonon and Fröhlich interaction of the LO phonon are taken into account. This model is successfully applied to the analysis of experimentally-observed emission line intensity ratios for excitons. This analysis reveals that the strong population exchange between the state of the principal quantum number n = 2 and the continuum takes place due to the increase in temperature. Further, the long experimental radiative lifetime component in the temporal PL decay curve up to 100 ns at room temperature (RT) is attributed to the shift of the population distribution to higher n states, which work as population reservoirs of the n = 1 state. Theoretical calculation using this model suggests that the dominant phonon mode in the excitation transfers from the n = 1 and 2 states shifts from the LA phonon to the LO phonon due to the increase in temperature from 130 K to 240 K. The PXR simulation model is feasible for the analysis of exciton-carrier dynamics and radiation efficiency analyses.

Semi-empirical metallicity calibrations based on ultraviolet emission lines of type-2 AGNs

We derived two semi-empirical calibrations between the metallicity of the Narrow Line Region (NLR) of type-2 Active Galactic Nuclei and the rest-frame of the N V$\lambda$1240/He II$\lambda1640$, C43=log[(C IV$\lambda1549$+C III]$\lambda1909$)/HeII$\lambda1640$] and C III]$\lambda1909$/C IV$\lambda1549$ emission-line intensity ratios. A metallicity-independent calibration between the ionization parameter and the C III]$\lambda1909$/C IV$\lambda1549$ emission-lines ratio was also derived. These calibrations were obtained comparing ratios of measured UV emission-line intensities, compiled from the literature, for a sample of 77 objects (redshift $0 \: < \: z \: < \: 3.8$) with those predicted by a grid of photoionization models built with the Cloudy code. Using the derived calibrations, it was possible to show that the metallicity estimations for NLRs are lower by a factor of about 2-3 than those for Broad Line Regions (BLRs). Besides we confirmed the recent result of the existence of a relation between the stellar mass of the host galaxy and its NLR metallicity. We also derived a $M-Z$ relation for the objects in our sample at $1.6 \: < \: z \: < \: 3.8$. This relation seems to follow the same trend as the ones estimated for Star Forming galaxies of similar high redshifts but for higher masses.

On the interplay between plasma discharge instability and formation of free-standing graphene nanosheets in a dual-channel microwave plasma torch at atmospheric pressure

The influence of the interplay between central (QC) and secondary (QS) channel gas flow, as well as delivered microwave power (PMW), during graphene nanosheet synthesis in a dual-channel electrode configuration of a microwave plasma torch at atmospheric pressure by ethanol decomposition was investigated. In the dual-channel configuration, plasma discharge can be sustained, even at high flow rates of ethanol, due to the separation of argon working and carrier gas. The plasma discharge instability was mainly influenced by an increase in the central channel flow, and a minor influence of secondary channel flow was also observed. With respect to the dependence on experimental conditions, the synthesized nanopowder consisted of amorphous carbon and nanocrystalline diamond nanoparticles, defective carbon nanosheets or few-layer graphene nanosheets. The synthesized nanosheets are rectangular in shape with a lateral size of several hundreds of nanometres and a few graphene layers thick, as shown by electron microscopy. Raman and x-ray photoelectron spectroscopy analysis of the synthesized nanosheets showed a good degree of graphitization, low oxygen content and increasing quality of graphene nanosheets with increasing microwave power. The number of defects in the synthesized nanosheets could be decreased by elongation of the graphene nanosheet assembly zone. An increase in the C2/C emission line intensity ratio correlated with a decrease in the number of defects in the graphene nanosheet structure. The achieved conversion yield of ethanol into graphene nanosheets was 8.3%, without negatively affecting the nanosheet quality.

Compositional depth profiles of the type 316 stainless steel undergone the corrosion in liquid lithium using laser-induced breakdown spectroscopy

Liquid metal lithium cause severe corrosion on the surface of metal structure material that used in the blanket and first wall of fusion device. Fast and accurate compositional depth profile measurement for the boundary layer of the corroded specimen will reveal the clues for the understanding and evaluation of the liquid lithium corrosion process as well as the involved corrosion mechanism. In this work, the feasibility of laser-induced breakdown spectroscopy for the compositional depth profile analysis of type 316 stainless steel which was corroded by liquid lithium in certain conditions was demonstrated. High sensitivity of LIBS was revealed especially for the corrosion medium Li in addition to the matrix elements of Fe, Cr, Ni and Mn by the spectral analysis of the plasma emission. Compositional depth profile analysis for the concerned elements which related to corrosion was carried out on the surface of the corroded specimen. Based on the verified local thermodynamic equilibrium shot-by-shot along the depth profile, the matrix effect was evaluated as negligible by the extracted physical parameter of the plasmas generated by each laser pulse in the longitudinal depth profile. In addition, the emission line intensity ratios were introduced to further reduce the impact on the emission line intensity variations arise from the strong inhomogeneities on the corroded surface. Compositional depth profiles for the matrix elements of Fe, Cr, Ni, Mn and the corrosion medium Li were constructed with their measured relative emission line intensities. The distribution and correlations of the concerned elements in depth profile may indicate the clues to the complicated process of composition diffusion and mass transfer. The results obtained demonstrate the potentiality of LIBS as an effective technique to perform spectrochemical measurement in the research fields of liquid metal lithium corrosion.