Assumption Of Local Thermodynamic Equilibrium Research Articles

Readdressing the UV solar variability with SATIRE-S: non-LTE effects

Context. Solar spectral irradiance (SSI) variability is one of the key inputs to models of the Earth’s climate. Understanding solar irradiance fluctuations also helps to place the Sun among other stars in terms of their brightness variability patterns and to set detectability limits for terrestrial exoplanets. Aims. One of the most successful and widely used models of solar irradiance variability is Spectral And Total Irradiance REconstruction model (SATIRE-S). It uses spectra of the magnetic features and surrounding quiet Sun that are computed with the ATLAS9 spectral synthesis code under the assumption of local thermodynamic equilibrium (LTE). SATIRE-S has been at the forefront of solar variability modelling, but due to the limitations of the LTE approximation its output SSI has to be empirically corrected below 300 nm, which reduces the physical consistency of its results. This shortcoming is addressed in the present paper. Methods. We replaced the ATLAS9 spectra of all atmospheric components in SATIRE-S with spectra that were calculated using the Non-LTE Spectral SYnthesis (NESSY) code. To compute the spectrum of the quiet Sun and faculae, we used the temperature and density stratification models of the FAL set. Results. We computed non-LTE contrasts of spots and faculae and combined them with the corresponding fractional disc coverages, or filling factors, to calculate the total and spectral irradiance variability during solar cycle 24. The filling factors have been derived from solar full-disc magnetograms and continuum images recorded by the Helioseismic and Magnetic Imager on Solar Dynamics Observatory (SDO/HMI). Conclusions. The non-LTE contrasts yield total and spectral solar irradiance variations that are in good agreement with empirically corrected LTE irradiance calculations. This shows that the empirical correction applied to the SATIRE-S total and spectral solar irradiance is consistent with results from non-LTE computations.

Decomposition mechanism and kinetics of iso-C4 perfluoronitrile (C4F7N) plasmas

Iso-C4 perfluoronitrile (C4F7N) is one of the most promising alternatives to SF6 for use in power equipment, such as high-voltage circuit breakers, due to its excellent electrical properties and environmentally friendly characteristics. The use of SF6 is being reduced because of its high global warming potential. To describe the physical and chemical processes occurring in the arc plasma in circuit breakers, both local thermodynamic equilibrium (LTE) and nonlocal chemical equilibrium (LCE) conditions have to be considered. The plasma composition of the arc core region can be calculated under the assumption of LTE by the method of minimization of the Gibbs free energy. The plasma composition of the arc boundary region or during the arc ignition period is not in LTE or LCE, so the use of a chemical kinetic model that considers the effects of the energy barrier in chemical reactions is required. Calculations for both conditions are presented for C4F7N. To develop the chemical kinetic model, the complete decomposition pathway and transition states were first reexamined and further developed. Based on the decomposition pathway, the rate constants of reactions were obtained according to the variational transition state theory method. The results obtained for the two cases provide a reference for the systematic understanding of the decomposition characteristics of C4F7N gas and for related engineering applications.

Simulating changes in shape of thermionic cathodes during operation of high-pressure arc discharges

A numerical model of current transfer to thermionic cathodes of high-pressure arc discharges is developed with account of deviations from local thermodynamic equilibrium occurring near the cathode surface, in particular, of the near-cathode space-charge sheath, melting of the cathode, and motion of the molten metal under the effect of the plasma pressure, the Lorentz force, gravity, and surface tension. Modelling results are reported for a tungsten cathode of an atmospheric-pressure argon arc and the computed changes in the shape of the cathode closely resemble those observed in the experiment. The modelling has shown that the time scale of change of the cathode shape during arc operation is very sensitive to the temperature attained by the cathode. The fact that the computed time scales conform to those observed in the experiment indicate that the model of non-equilibrium near-cathode layers in high-pressure arc discharges, employed in this work, predicts the cathode temperature for a given arc current with adequate accuracy. In contrast, modelling based on the assumption of local thermodynamic equilibrium in the whole arc plasma computation domain up to the cathode surface could hardly produce a similar agreement.

Numerical thermofluid simulation of a decaying arc behavior in CO2/O2/C5F10O (C5‐PFK) considering more than nona‐atomic molecules

AbstractThe present article describes numerical thermofluid simulation results on decaying arc behavior in 80%CO2 + 10%O2 + 10%C5F10O (C5‐PFK) gas considering molecules constituted with more than 9 atoms in a nozzle space on the assumption of local thermodynamic equilibrium (LTE) condition. The gas mixture 80%CO2 + 10%O2 + 10%C5F10O (C5‐PFK) is one of the candidate alternatives for SF6 in a gas circuit breaker. First, we calculated 80%CO2 + 10%O2 + 10%C5F10O (C5‐PFK) arc characteristics only by considering less than 8‐atom molecules. However, it seems possible to produce more than nona‐atomic molecules in the low‐temperature region in 80%CO2 + 10%O2 + 10%C5F10O (C5‐PFK) arcs. The present work further calculated the equilibrium composition of this gas mixture at 0.1 MPa with taking account more than nona‐atomic molecules. Furthermore, their thermodynamic and transport properties were also computed with collision integrals between species considered. Using these properties, the arc temperature and gas flow fields were calculated using two‐dimensional LTE model for a free recovery condition from dc 50 to 0 A. Results showed that a similar temperature decay was obtained for arcs in the 80%CO2 + 10%O2 + 10%C5F10O (C5‐PFK) gas mixture to that for arcs in 100%CO2 gas. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Calculation and analysis of the thermophysical properties of C5F10O-N2 mixtures

C5-PFK (C5F10O), with high dielectric strength and low global warming potential, is the new environmental-friendly potential alternative gases to SF6. In order to reduce its excessively high liquefaction temperature while retaining its excellent properties, a certain amount of buffer gases, such as N2 can be added to it. Therefore, to understand the plasma behavior of under C5F10O-N2 mixtures, the composition, thermodynamic properties and transport properties of the C5F10O-N2 mixtures in a temperature range of 300K to 30000K and a pressure range of 0.1 MPa to 0.8 MPa is calculated under the assumption of local thermodynamic equilibrium. Then, the influence of mixing ratios and pressures are analyzed. The results can be used to determine the optimal proportion of C5F10O-N2 mixtures. Several peaks of the specific heat can be observed below 5000K, which could be a favorable factor for arc quenching.

Quantitative elemental analysis of high silica bauxite using calibration-free laser-induced breakdown spectroscopy.

Bauxite is a primary ore of aluminum. Precise information about bauxite mineralogical composition is challenging and crucial for efficient aluminum extraction and for the determination of its appropriateness for different industrial applications. For the qualitative and quantitative analysis of bauxite ore, we performed laser-induced breakdown spectroscopy (LIBS) in conjunction with x-ray diffraction (XRD), x-ray fluorescence spectroscopy (XRF), scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). Analysis of the acquired optical emission spectrum revealed the presence of Si, Al, Fe, K, Ti, Ca, Mg, Na, Cr, and Sr. The plasma temperature and electron number density values estimated using Boltzmann plot and Stark-broadening line profile methods were 5600K and 7.65×1017 cm-3, respectively. In the present study we show that a calibration-free LIBS method presents a powerful solution, enabling quantitative analysis of multi-element bauxite ore better than traditional analytical techniques. The bauxite quantification obtained using CF-LIBS under the assumption of local thermodynamic equilibrium and optically thin plasma was Si=47.31%, Al=31.90%, Fe=16.54%, K=2.45%, Ti=1.64%, and Ca=0.16%, and its comparison with the outcome from XRD, XRF, SEM-EDS, and FTIR not only assisted but potentially enhanced the mineralogical composition understanding of bauxite ore in the present study.

Application of Calibration-Free Boltzmann Plot Method for Composition and Pressure Measurement in Argon Free-Burning Arcs

Arc plasmas have been extensively studied, experimentally and by means of modeling, due to their wide range of applications. In this article, a calibration-free Boltzmann plot method was applied to measure the species composition and pressure in the arc plasmas based on the assumption of local thermodynamic equilibrium and only single ionization of atoms. Experiments were performed on the argon free-burning arcs at two different pressures. Firstly, several Ar I and Ar II spectral lines were utilized to draw the Boltzmann plot. Then, the plasma temperatures were obtained by three different methods, the Boltzmann plot method, two-line Saha–Boltzmann plot method, and the Fowler–Milne method. The species concentration was calculated using the intercepts with ordinate in the Boltzmann plot. Combined with the electron number density determined from the Stark broadening of Ar I 696.54 nm, arc pressures are calculated based on the equation of state. The measured species concentration and pressures are in good agreement with the theoretical results, indicating that the used method is reliable for further arc plasma applications.

Non-LTE analysis of K I in late-type stars

Context. Older models of Galactic chemical evolution (GCE) predict [K/Fe] ratios as much as 1 dex lower than those inferred from stellar observations. Abundances of potassium are mainly based on analyses of the 7698 Å resonance line, and the discrepancy between GCE models and observations is in part caused by the assumption of local thermodynamic equilibrium (LTE) in spectroscopic analyses. Aims. We study the statistical equilibrium of K I, focusing on the non-LTE effects on the 7698 Å line. We aim to determine how non-LTE abundances of potassium can improve the analysis of its chemical evolution, and help to constrain the yields of GCE models. Methods. We construct a new model K I atom that employs the most up-to-date atomic data. In particular, we calculate and present inelastic e+K collisional excitation cross-sections from the convergent close-coupling (CCC) and the B-Spline R-matrix (BSR) methods, and H+K collisions from the two-electron model (LCAO). We constructed a fine, extended grid of non-LTE abundance corrections based on 1D MARCS models that span 4000 < Teff∕K < 8000, 0.50 < log g < 5.00, − 5.00 < [Fe/H] < + 0.50, and applied the corrections to potassium abundances extracted from the literature. Results. In concordance with previous studies, we find severe non-LTE effects in the 7698 Å line. The line is stronger in non-LTE and the abundance corrections can reach approximately − 0.7 dex for solar-metallicity stars such as Procyon. We determine potassium abundances in six benchmark stars, and obtain consistent results from different optical lines. We explore the effects of atmospheric inhomogeneity by computing for the first time a full 3D non-LTE stellar spectrum of K I lines for a test star. We find that 3D modeling is necessary to predict a correct shape of the resonance 7698 Å line, but the line strength is similar to that found in 1D non-LTE. Conclusions. Our non-LTE abundance corrections reduce the scatter and change the cosmic trends of literature potassium abundances. In the regime [Fe/H] ≲−1.0 the non-LTE abundances show a good agreement with the GCE model with yields from rotating massive stars. The reduced scatter of the non-LTE corrected abundances of a sample of solar twins shows that line-by-line differential analysis techniques cannot fully compensate for systematic LTE modelling errors; the scatter introduced by such errors introduces a spurious dispersion to K evolution.

A Zel’dovich–von Neumann–Döring-like detonation wave in a multi-temperature mixture

The detonation wave structure is analysed in a binary mixture undergoing a reversible chemical reaction represented by$A_{r}\rightleftharpoons A_{p}$. It is assumed that the flow satisfies the proper basic assumptions of the Zel’dovich–von Neumann–Döring (ZND) detonation model, namely the flow is one-dimensional and the shock is represented by a jump discontinuity, but the assumption of local thermodynamic equilibrium is disregarded. This allows us to deeply investigate the coupling between the detonation structure of overdriven detonations and its chemical kinetics. The thermodynamic non-equilibrium effects are taken into account in the mathematical description, using the model of a multi-temperature mixture developed within extended thermodynamics, which has been proved to be consistent with a kinetic theory approach. The reaction rate is then enriched with terms that take into account the temperatures of the constituents. The results show that the temperature difference between components within the detonation wave structure, which describes thermodynamic non-equilibrium, is driven by the chemical reaction. Numerical computations confirm the existence of non-monotonic profiles in the reaction zone of overdriven detonations which are sensitive to changes in the activation energy and reaction heat.

Estimation of plasma parameters in the process of micro-scale powder plastic and characteristics of its products

The temperature and density of plasma jets were estimated with a Boltzmann plot and Stark broadening of Ar I (696.54 nm) lines by optical emission spectroscopy (OES) in the process of plasma plastic, and the morphology and microstructure of tungsten (W) powders were investigated by scanning electron microscope (SEM) and x-ray Diffraction (XRD), respectively. The results show that the assumption of local thermodynamic equilibrium (LTE) was invalid at the end of the plasma jets, and earlier than this after the injection of tungsten powder. The temperature and electron density of the plasma jets were up to about T = 6797 K with Qc = 50 slpm and ne = 1.05 × 1016 cm−3 with Qs = 115 slpm at Z = 60 mm, respectively, and both dropped rapidly with the injected tungsten powders of 20 μm. After the plasma plastic process, the spherical tungsten powders were prepared and there were some satellite particles on the surface of the spherical products. The tungsten powders were both composed of a single equilibrium α-W phase with a body centered cubic (bbc) crystal structure before and after plasma treatment.

Spectral analysis of mint (pudina) using laser-induced breakdown spectroscopy and inductively coupled plasma/atomic emission spectroscopy

In the current study, pulsed Nd:YAG laser-induced breakdown spectroscopy (LIBS) was successfully applied, at 532 nm with a suitable detector, for the spectral analysis of mint (domestic mint and wild mint) available in Pakistan. From the spectral emissions of the mint plasmas recorded with the spectrometer (LIBS2000+, Ocean Optics, Inc.), 17 elements were identified in the domestic mint whereas the wild mint was observed to have 18 different elements, comprising both nutritional elements and toxic metals. Prior to recording the spectral emissions, the sensitivity of our LIBS detection was enhanced by optimizing various LIBS parameters. Under ambient environments, a laser pulse irradiance of about 2.0 × 1011 W cm−2 was employed for the generation of the plasmas on the surfaces of the target samples. The quantitative analyses were performed via calibration curves drawn for all the elements through standard samples prepared in a known concentration in the mint matrix, as well as by a weight percentage method under the assumptions of local thermodynamic equilibrium and optically thin plasma. The electron temperature and number density were determined through the Boltzmann plot method and stark broadened line profile method, respectively, using Ca-I spectral lines. Furthermore, to verify the precision of our LIBS findings, the abundance of each element in the mint samples was also estimated by means of a standard analytical tool, such as inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The outcomes of the LIBS system were found to be in good agreement with the results of ICP/AES statistically, which guarantees that the method is reliable in the illustration and detection of both nutritional and toxic chemical differences in the mint samples, and is hence a step forward in securing human health through environmental and agricultural development.

On the iron ionization balance of cool stars

Abstract High-resolution spectroscopic studies of solar-type stars have revealed higher iron abundances derived from singly ionized species compared to neutral, violating the ionization equilibrium under the assumption of local thermodynamic equilibrium. In this work, we investigate the overabundances of Fe ii lines reported in our previous work for a sample of 451 solar-type HARPS stars in the solar neighborhood. The spectroscopic surface gravities of this sample, which emerge from the ionization balance, appear underestimated for the K-type stars. In order to understand this behaviour, we search our Fe ii line list for unresolved blends and outliers. First, we use the Vienna Atomic Line Database to identify possible unresolved blends around our lines and calculate which ones are strong enough to cause overestimations in the equivalent width measurements. Second, for our sample we use reference parameters (effective temperature and metallicity) and the Gaia DR2 parallaxes to derive surface gravities (trigonometric gravities) and calculate the Fe i and Fe ii abundances from different line lists. We exclude the Fe ii lines which produce overabundances above 0.10 dex. The derived surface gravities from the clean line list are now in agreement with the trigonometric. Moreover, the difference between Fe i and Fe ii abundance does not show now a correlation with the effective temperature. Finally, we show that the ionization balance of Ti can provide better estimates of surface gravities than iron. With this analysis, we provide a solution to the ionization balance problem observed in the atmospheres of cool dwarfs.

Arepo-rt: radiation hydrodynamics on a moving mesh

We introduce AREPO-RT, a novel radiation hydrodynamic (RHD) solver for the unstructured moving-mesh code AREPO. Our method solves the moment-based radiative transfer equations using the M1 closure relation. We achieve second order convergence by using a slope limited linear spatial extrapolation and a first order time prediction step to obtain the values of the primitive variables on both sides of the cell interface. A Harten-Lax-Van Leer flux function, suitably modified for moving meshes, is then used to solve the Riemann problem at the interface. The implementation is fully conservative and compatible with the individual timestepping scheme of AREPO. It incorporates atomic Hydrogen (H) and Helium (He) thermochemistry, which is used to couple the ultra-violet (UV) radiation field to the gas. Additionally, infrared radiation is coupled to the gas under the assumption of local thermodynamic equilibrium between the gas and the dust. We successfully apply our code to a large number of test problems, including applications such as the expansion of ${\rm H_{II}}$ regions, radiation pressure driven outflows and the levitation of optically thick layer of gas by trapped IR radiation. The new implementation is suitable for studying various important astrophysical phenomena, such as the effect of radiative feedback in driving galactic scale outflows, radiation driven dusty winds in high redshift quasars, or simulating the reionisation history of the Universe in a self consistent manner.

Numerical simulation of mixture gas arc of Ar-O<sub>2</sub>

Mixture gas arcs are used extensively in welding manufacturing. A two-dimensional steady mathematical model for Ar-O<sub>2</sub> mixture gas arc is developed to understand further the heat and mass transfer of the mixture gas arc. The model is based on the assumption of local thermodynamic equilibrium, and the thermodynamic parameters and transport coefficients are dependent on both the temperature and the oxygen content. In the present model, the diffusion between the argon species and oxygen species is depicted by the approach of the combined diffusion coefficient, i. e. the mixture gas arc is simplified into two different species, and the diffusion between them is formulated by combined ordinary diffusion coefficient and combined temperature diffusion coefficient; the oxygen distribution and its influence on the temperature and flow field of the arc are investigated for two different current conditions. It is shown that the oxygen species presents significant non-uniform distribution for argon gas mixed with 5% oxygen; the oxygen content is higher than that in mixed shielding gas in the regions close to the electrodes and arc axis, while its content is lower than that of the mixed shielding gas in other regions. For high current, oxygen concentrates more to the flat anode, while it concentrates more to tungsten cathode for low current. For both cases, oxygen content is inhomogeneous in the region 0.1 mm above the anode. The 5% oxygen mixed in argon constricts the arc plasma to some extent and thus raises the arc temperature as well as the plasma flow velocity.

A timeline for massive star-forming regions via combined observation of o-H2D+ and N2D+

Context. In cold and dense gas prior to the formation of young stellar objects, heavy molecular species (including CO) are accreted onto dust grains. Under these conditions H3+ and its deuterated isotopologues become more abundant, enhancing the deuterium fraction of molecules such as N2H+ that are formed via ion-neutral reactions. Because this process is extremely temperature sensitive, the abundance of these species is likely linked to the evolutionary stage of the source. Aims. We investigate how the abundances of o-H2D+ and N2D+ vary with evolution in high-mass clumps. Methods. We observed with APEX the ground-state transitions of o-H2D+ near 372 GHz, and N2D+(3–2) near 231 GHz for three massive clumps in different evolutionary stages. The sources were selected within the G351.77–0.51 complex to minimise the variation of initial chemical conditions, and to remove distance effects. We modelled their dust continuum emission to estimate their physical properties, and also modelled their spectra under the assumption of local thermodynamic equilibrium to calculate beam-averaged abundances. Results. We find an anticorrelation between the abundance of o-H2D+ and that of N2D+, with the former decreasing and the latter increasing with evolution. With the new observations we are also able to provide a qualitative upper limit to the age of the youngest clump of about 105 yr, comparable to its current free-fall time. Conclusions. We can explain the evolution of the two tracers with simple considerations on the chemical formation paths, depletion of heavy elements, and evaporation from the grains. We therefore propose that the joint observation and the relative abundance of o-H2D+ and N2D+ can act as an efficient tracer of the evolutionary stages of the star-formation process.

3D time-dependent numerical simulation for atmospheric plasma spraying

The coating quality and reproducibility of plasma spraying are significantly affected by the characteristic of plasma jet that is closely related to the arc root attachment. In this study, a 3D time-dependent numerical model based on the Local Thermodynamic Equilibrium (LTE) assumption was developed to investigate the arc dynamics and its effect on the distributions of temperature and flow field both inside and outside of the torch. The results show that there is the coexistence of multiple arc roots, and the particular attachment location of plasma arc leads to a significant asymmetry in distributions of temperature, velocity as well as electric potential and field strength. The continuous movement of the plasma arc not only caused the fluctuations of the arc voltage drop, but also resulted in the temporal variations of the plasma temperature and velocity. Moreover, the predicted temperature and velocity distributions of plasma jet were in good agreement with experimental measurements.

Numerical investigation of transient, low-power metal vapour discharges occurring in near limit ignitions of flammable gas

This article presents an investigation of a transient (30 μs–) electrical discharge in metal vapour with low voltage () and current (), drawn between two separating electrodes. Discharges of this type are rarely studied, but are important in electrical explosion safety, as they can ignite flammable gasses. An empirical model is developed based on transient recordings of discharge voltages and currents and high speed broadband image data. The model is used for predicting the electrical waveforms and spatial power distribution of the discharge. The predicted electrical waveforms show good accuracy under various scenarios. To further investigate the underlying physics, the model is then incorporated into a simplified 3-D gas dynamics simulation of the discharge occurring in a flammable atmosphere. This simulation includes chemical reactions, molecular diffusion, heat transfer and evaporation of metal from the electrode surface. The local thermodynamic equilibrium (LTE) assumption is next used to calculate electrical conductivity from the field outputs of the simulation, which in turn is integrated to produce electrical resistance over time. This resistance is then compared to that implied by the voltage and current waveforms predicted by the empirical model. The two methods produce differing estimates, demonstrating that the studied discharge very likely deviates from LTE. Finally, assuming that electrical conductivity is approximately independent of the heavy particle temperature, the empirical model is used together with the calculated electrical conductivities to estimate the electron temperatures present in the discharge.

Elemental analysis of limestone by laser-induced breakdown spectroscopy, scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and electron probe microanalysis

Limestone, a sedimentary rock-forming mineral is a source of lime and is important industrially as it usually contains +95% calcium carbonate and <5% impurities. The presence of these impurities can cause problems while accessing the different applications of limestone requiring high chemical purity. Due to its great significance and multiple applications, the qualitative and quantitative analysis of limestone is highly desirable. The analysis of the emission spectrum obtained at the fundamental harmonic (1064 nm) of Q-switched Nd:YAG laser revealed the presence of Ca, Si, Al, Mg, Na, Fe, Ti, K, Sr and S with varying intensities. The Boltzmann plot method used to deduce the excitation temperature, and the electron number density value measured by the Stark broadening method resulted in the ranges from 4091–4231 K and (1.2–6.4) × 1016 cm−3, respectively. The quantitative analysis has been performed using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS) technique based on the assumption of local thermodynamic equilibrium and optically thin plasma. The results of the CF-LIBS technique were compared to the measurements of other more standard analytical methods such as scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and electron probe microanalysis with good agreement.

SMA molecular line survey towards the massive star-forming region G10.6−0.4 in W31 complex

Line surveys of complex molecules with millimeter and sub-millimeter telescopes are important for probing the physical and chemical environments of massive star forming regions (MSFRs). We present a molecular line survey with the Submillimeter Array (SMA) in the frequency ranges of 220.3–222.3 GHz and 230.3–232.3 GHz toward G10.6−0.4, the brightest star forming core in the W31 complex. Ninety-nine transitions from 22 molecular species and their isotopologues are identified. The moment 0 images of typical molecules show a compact core which is concentrated at the continuum peak position. Based on the local thermodynamic equilibrium assumption, the molecular line data are modeled. The rotational temperatures of those molecular species range from 96 to 178 K and their column densities range from 2.0 × 1014 to 3.7 × 1017 cm−2. The observational data suggest that all complex molecules are located in a warm environment. Chemical environments of the molecules are discussed. We compared molecular abundances and gas temperatures in G10.6−0.4 with those in other MSFRs, and found that gas temperatures and fractional abundances of specific molecules in G10.6−0.4 are similar to the typical MSFR W51 North, suggesting that there are similar physical and chemical environments in these two MSFRs.

Chemical kinetics analysis of two C5-perfluorinated ketone (C5 PFK) thermal decomposition products: C4F7O and C3F4O

SF6 has been designated as a greenhouse gas by the Kyoto Protocol because of its high global warming potential. C5-perfluorinated ketone (C5F10O or C5-PFK) has excellent insulation properties and environmental characteristics, and has been chosen as an alternative gas to SF6. Calculation of thermal decomposition is usually based on local thermodynamic equilibrium (LTE) and local chemical equilibrium assumptions. However, the composition may not reach chemical equilibrium, particularly at lower temperatures and high rates of temperature increase. In order to compare the chemical non-equilibrium and local thermodynamic equilibrium compositions, a chemical kinetic model is used to calculate time evolution of composition; this considers the effects of the energy barrier in chemical reactions. To obtain the required data for the model, which is necessary because of the limited research on reaction rates in C5-PFK decomposition, the methods of computational chemistry are used to calculate transition states and reaction rates. The LTE composition is calculated using Gibbs free energy minimization. Calculations are presented for two possible C5-PFK thermal decomposition products, C4F7O and C3F4O. The result indicates that chemical kinetics is required to calculate the dissociation of C5-PFK at low temperatures, such as occur during arc ignition and near the arc boundary.