scholarly journals Calculation of the ionization state for LTE plasmas using analytical potentials

1999 ◽  
Vol 17 (4) ◽  
pp. 635-647 ◽  
Author(s):  
J.G. RUBIANO ◽  
R. RODRÍGUEZ ◽  
J.M. GIL ◽  
P. MARTEL ◽  
E. MÍNGUEZ
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Atomic Data ◽  
Partition Functions ◽  
Ionization State ◽  
Saha Equation ◽  
Analytical Potential ◽  
Plasma Effects

In this work, the Saha equation is solved using atomic data provided by means of analytical potentials to calculate the ionization state and ion abundances for local thermodynamic equilibrium (LTE) plasmas of Al, Fe, and Au. The plasma effects are taking into account using an analytical potential which includes plasma effects. The problem of the cut off partition functions in the Saha equation is also analyzed using three different criteria. Finally, some opacity calculations are performed.

scholarly journals Calculation of the ionization state for LTE plasmas using a new relativistic-screened hydrogenic model based on analytical potentials

2002 ◽  
Vol 20 (1) ◽  
pp. 145-151 ◽  
Author(s):  
J.G. RUBIANO ◽  
R. RODRÍGUEZ ◽  
J.M. GIL ◽  
P. MARTEL ◽  
E. MÍNGUEZ
Keyword(s):  
Atomic Structure ◽  
Maxwellian Distribution ◽  
Atomic Data ◽  
Ionization State ◽  
Free Electrons ◽  
Saha Equation ◽  
Model Based ◽  
Plasma Effects ◽  
Self Consistent ◽  
Hydrogenic Model

In this work, the Saha equation is solved using atomic data provided by means of a new relativistic-screened hydrogenic model based on analytical potentials to calculate the ionization state and ion abundance for LTE iron plasmas. The plasma effects on the atomic structure are taken into account by including the classical continuum lowering correction of Stewart and Pyatt. For high density, the Saha equation is modified to consider the degeneration of free electrons using the Fermi–Dirac statistics instead of the Maxwellian distribution commonly used. The results are compared with more sophisticated self-consistent codes.

scholarly journals On the violation of local thermodynamic equilibrium in the plasma jet of an argon arc two-jet plasmatron

2019 ◽  
Vol 85 (1II)) ◽  
pp. 145-150
Author(s):  
A. S. Cherevko ◽  
A. A. Morozova
Keyword(s):  
Energy Level ◽  
Equilibrium State ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Plasma Jet ◽  
Saha Equation ◽  
Radiation Processes ◽  
Unconventional Method

The degree and nature of the violation of local thermodynamic equilibrium (LTE) in the analytical zone of a plasma jet generated by an argon arc two-jet plasmatron (TJP) was estimated using an unconventional method based on determination of the nonequilibrium parameterbiequal to the ratio of the experimentally determined actual population of the energy level (ni) of the element to the population of the same level calculated from the Saha equation (nis). Partial ionizing deviation of plasma under study from the equilibrium state takes place only when low-lying atomic levels are overpopulated. The distinct dependence ofbion the ionization potential of the considered element (e.g., Ca, Mg, and Be) is shown. The results were interpreted in the light of the increasing role of radiation processes upon excitation of spectra in the argon arc two-jet plasmatron.

scholarly journals Non-local thermodynamic equilibrium line formation for Si i–ii–iii in A–B stars and the origin of Si ii emission lines in ι Her

2020 ◽  
Vol 493 (4) ◽  
pp. 6095-6108 ◽  
Author(s):  
Lyudmila Mashonkina
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Emission Lines ◽  
Atomic Data ◽  
Line Formation ◽  
Atmospheric Parameters ◽  
B Stars ◽  
Non Local ◽  
Effective Temperatures ◽  
Model Atom

ABSTRACT A comprehensive model atom was developed for Si i–ii–iii using the most up-to-date atomic data available so far. Based on non-local thermodynamic equilibrium (NLTE) line formation for Si i, Si ii and Si iii and high-resolution observed spectra, we determined the NLTE abundances for a sample of nine unevolved A9–B3 type stars with well-determined atmospheric parameters. For each star, NLTE reduces the line-to-line scatter for Si ii substantially compared with the LTE case and leads to consistent mean abundances from lines of different ionization stages. In the hottest star of our sample, ι Her, Si ii is subject to overionization that drives emission in the lines arising from the high-excitation doublet levels. Our NLTE calculations reproduced 10 emission lines of Si ii observed in ι Her. The same overionization effect leads to greatly weakened Si ii lines, which are observed in absorption in ι Her. Large positive NLTE abundance corrections (up to 0.98 dex for 5055 Å) were useful for achieving consistent mean abundances from lines of the two ionization stages, Si ii and Si iii. It was found that NLTE effects are overestimated for the Si ii 6347, 6371 Å doublet in ι Her, while the new model atom works well for cooler stars. At this stage, we failed to understand this problem. We computed a grid of the NLTE abundance corrections for lines of Si i, Si ii and Si iii in model atmospheres with effective temperatures and surface gravities characteristic of unevolved A–B type stars.

Transient conditions in inductively heated plasmas: thermodynamic equilibrium and temperature measurements

1982 ◽  
Vol 60 (6) ◽  
pp. 886-892 ◽  
Author(s):  
Paul Meubus
Keyword(s):  
Thermodynamic Equilibrium ◽  
Decay Time ◽  
Concentration Distribution ◽  
Local Thermodynamic Equilibrium ◽  
Energy Levels ◽  
Argon Plasma ◽  
Partition Functions ◽  
Transient Conditions ◽  
Gas Interactions ◽  
Catalytic Effects

A study has been made on transient extinction conditions in an inductively heated argon plasma. It was observed that local thermodynamic equilibrium (LTE) conditions do exist between the metastable 3P2 level and upper energy levels, so that during the decay time it is possible to determine a meaningful temperature, using the 3P2 level as a fundamental level and the partition functions being calculated accordingly. Together with the temperature determination, a concentration distribution of argon metastables was obtained.Studies of this type are useful for the investigation of quenching processes in plasmas, affecting favorably chemical reactions or solid–gas interactions, thus leading to enhanced catalytic effects or modifications of solid particle structures which are liable to generate new electrical, thermal, etc. properties of interest.

scholarly journals Summary of the Joint Discussion: Atomic Data of Importance for Ultraviolet and X-Ray Astronomy

1971 ◽  
Vol 2 ◽  
pp. 580-583
Author(s):  
A. G. Hearn
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Ground Level ◽  
Experimental Methods ◽  
Present Knowledge ◽  
Atomic Data ◽  
The Sun ◽  
X Ray ◽  
Lyman Continuum

AbstractThis Joint Discussion is in two parts. The first part is a description of recent observations which illustrate the need for atomic data and the second part is a description of what atomic data are available or could readily be produced by the latest theoretical and experimental methods. The purpose of this summary is to highlight the immediate requirements for atomic data of current observations which are not met by our present knowledge and thereby indicate where further work is necessary in providing atomic data.Although this is a discussion of atomic data the problems of assuming local thermodynamic equilibrium have inevitably been raised. The importance of considering whether departures from LTE are significant or not in the interpretation of observations is is clearly illustrated by the work of the Harvard group on the Lyman continuum emitted by the Sun which has shown a departure coefficient as large as 200 for the ground level of hydrogen.

scholarly journals The Opacity Project and the Iron Project

1996 ◽  
Vol 152 ◽  
pp. 569-576
Author(s):  
Anil K. Pradhan
Keyword(s):  
Recent Work ◽  
Thermodynamic Equilibrium ◽  
Large Scale ◽  
Local Thermodynamic Equilibrium ◽  
Atomic Data ◽  
Data Sets ◽  
Iron Ions ◽  
Theoretical Methods ◽  
Work Related ◽  
Ionization Balance

Systematic and large-scale calculation of accurate plasma opacities and atomic data by the Opacity Project and the Iron Project has applications in many areas of astrophysics. Analysis of EUVE observations using monochromatic opacities of elements calculated by the Opacity Project is described. Theoretical methods and atomic calculations are discussed briefly. Recent work related to ionization balance, photoionization and recombination, and the modeling of plasmas in local thermodynamic equilibrium (LTE) and non-LTE are discussed. New calculations for the important iron ions, under the Iron Project, are also described and their relevance to the more extensive non-LTE calculations is pointed out. The comprehensive radiative and collisional data sets from the Opacity and the Iron Projects should be applicable to a large number of sources in the EUV and other wavelength regions.

scholarly journals Local thermodynamic equilibrium in a laser-induced plasma channel formed by interaction of femtosecond laser radiation with argon

2021 ◽  
Vol 2131 (5) ◽  
pp. 052090
Author(s):  
D A Kochuev ◽  
A F Galkin ◽  
A S Chernikov ◽  
R V Chkalov ◽  
A A Voznesenskaya ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Femtosecond Laser ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Plasma Channel ◽  
Necessary Condition ◽  
Femtosecond Laser Radiation ◽  
Free Electrons ◽  
Saha Equation ◽  
Laser Induced Plasma

Abstract In this paper, we estimate the possibility of applying local thermodynamic equilibrium conditions for a laser-induced plasma channel formed by femtosecond laser radiation in an argon medium at different pressures. The presence of a local thermodynamic equilibrium was determined on the basis of the time of heat exchange of electrons with argon atoms. The Saha equation is used to estimate the concentration of free electrons, the temperature of the laser-induced plasma channel, and its conductivity. A necessary condition for using this ratio was the presence of a state of local thermodynamic equilibrium in the plasma under study.

Blackbody Radiation, Boltzmann Statistics, Temperature, and Thermodynamic Equilibrium

2017 ◽  
Author(s):  
Kelly Chance ◽  
Randall V. Martin
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Photophysical Properties ◽  
Blackbody Radiation ◽  
Boltzmann Constant ◽  
Noise Sources ◽  
Atmospheric Molecules ◽  
Tightly Coupled ◽  
Boltzmann Statistics ◽  
Planck’S Law

Blackbody radiation, temperature, and thermodynamic equilibrium give a tightly coupled description of systems (atmospheres, volumes, surfaces) that obey Boltzmann statistics. They provide descriptions of systems when Boltzmann statistics apply, either approximately or nearly exactly. These apply most of the time in the Earth’s stratosphere and troposphere, and in other planetary atmospheres as long as the density is sufficient that collisions among atmospheric molecules, rather than photochemical and photophysical properties, determine the energy populations of the ensemble of molecules. Thermodynamic equilibrium and the approximation of local thermodynamic equilibrium are introduced. Boltzmann statistics, blackbody radiation, and Planck’s law are described. The chapter introduces the Rayleigh-Jeans limit, description of noise sources as temperatures, Kirchoff’s law, the Stefan-Boltzmann constant, and Wien’s law.

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