Studies of emission spectra in helium plasmas at atmospheric pressure and local thermodynamical equilibrium

For material stratified in parallel planes in local thermodynamical equilibrium we have Milne's well-known result thatwhere πF is the constant net integrated flux of radiation, τ is the optical depth and B is the “ergiebigkeit” which is related to the temperature T by the relationσ being the Stefan-Boltzmann constant. If we define the effective temperature by the relationwe have from (1)where T1 is the temperature ar τ = 1. In this note we establish a similar result for extended photospheres where the curvature of the outer layers is properly taken into account.

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Quenching rates and critical densities of c-C3H2

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319006379 ◽

2019 ◽

Vol 15 (S350) ◽

pp. 148-151

Author(s):

Malek Ben Khalifa ◽

Emna Sahnoun ◽

Silvia Spezzano ◽

Laurent Wiesenfeld ◽

Kamel Hammami ◽

...

Keyword(s):

Potential Energy Surfaces ◽

Full Potential ◽

Thermodynamical Equilibrium ◽

Medium Temperature ◽

Permanent Electric Dipole Moment ◽

Temperature Regimes ◽

Wide Range ◽

History Of ◽

Energy Surfaces ◽

Local Thermodynamical Equilibrium

AbstractCyclopropenylidene,, is a simple hydrocarbon, ubiquitous in astrophysical gases, and possessing a permanent electric dipole moment. Its readily observed multifrequency rotational transitions make it an excellent probe for the physics and history of interstellar matter. The collisional properties of with He are presented here. We computed the full Potential Energy Surfaces, and we perform quantum scattering in order to provide rates of quenching and excitation for low to medium temperature regimes. We discuss issues with the validity of the usual Local Thermodynamical Equilibrium assumption, and also the intricacies of the spectroscopy of an asymmetric top. We present the wide range of actual critical densities, as recently observed.

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Electrical and spectral property of cold arc plasma at atmospheric pressure

Journal of Plasma Physics ◽

10.1017/s0022377812000463 ◽

2012 ◽

Vol 78 (6) ◽

pp. 617-620

Author(s):

YUAN ZHONG-CAI ◽

SHI JIA-MING ◽

CHEN ZONG-SHENG ◽

XU BO

Keyword(s):

Atmospheric Pressure ◽

Arc Discharge ◽

Rotational Temperature ◽

Molecular Nitrogen ◽

Atmospheric Pressure Plasma ◽

Emission Spectra ◽

Optical Emission ◽

Plasma Jet ◽

Ambient Air ◽

Arc Plasma

AbstractAn atmospheric pressure plasma jet is generated with a cold arc discharge in ambient air. The current-voltage characteristics and optical emission spectra of plasma discharges are investigated. The molecular nitrogen (N2), hydroxyl radical (OH), and oxygen atom (O) are observed and analyzed. Based on the best fit of the simulated spectra of N2 (C3∏u+ − B3∏g+) band and OH (A2∑+ − X2∏) band transition and the experimentally recorded spectra, the rotational temperature and the vibrational temperature of atmospheric pressure cold arc plasma jet (APCAPJ) are estimated.

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A detailed study of lithium in 107 CHEPS dwarf stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731547 ◽

2018 ◽

Vol 611 ◽

pp. A27 ◽

Cited By ~ 8

Author(s):

Ya. V. Pavlenko ◽

J. S. Jenkins ◽

O. M. Ivanyuk ◽

H. R. A. Jones ◽

B. M. Kaminsky ◽

...

Keyword(s):

Isotopic Ratio ◽

Small Sample Size ◽

Small Sample ◽

Thermodynamical Equilibrium ◽

Lithium Abundance ◽

Dwarf Stars ◽

Upper Limits ◽

Resonance Doublet ◽

Non Local ◽

Local Thermodynamical Equilibrium

Context. We report results from lithium abundance determinations using high resolution spectral analysis of the 107 metal-rich stars from the Calan-Hertfordshire Extrasolar Planet Search programme. Aims. We aim to set out to understand the lithium distribution of the population of stars taken from this survey. Methods. The lithium abundance taking account of non-local thermodynamical equilibrium effects was determined from the fits to the Li I 6708 Å resonance doublet profiles in the observed spectra. Results. We find that a) fast rotators tend to have higher lithium abundances; b) log N(Li) is higher in more massive and hot stars; c) log N(Li) is higher in stars of lower log g; d) stars with the metallicities >0.25 dex do not show the lithium lines in their spectra; e) most of our planet hosts rotate slower; and f) a lower limit of lithium isotopic ratio is 7Li/6Li > 10 in the atmospheres of two stars with planets (SWP) and two non-SWP stars. Conclusions. Measurable lithium abundances were found in the atmospheres of 45 stars located at distances of 20−170 pc from the Sun, for the other 62 stars the upper limits of log N(Li) were computed. We found well defined dependences of lithium abundances on Teff, V sin i, and less pronounced for the log g. In case of V sin i we see two sequences of stars: with measurable lithium and with the upper limit of log N(Li). About 10% of our targets are known to host planets. Only two SWP have notable lithium abundances, so we found a lower proportion of stars with detectable Li among known planet hosts than among stars without planets. However, given the small sample size of our planet-host sample, our analysis does not show any statistically significant differences in the lithium abundance between SWP and stars without known planets.

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Non-local thermodynamical equilibrium abundance analysis of singly ionized praseodymium for the Sun

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1825 ◽

2020 ◽

Vol 496 (4) ◽

pp. 5361-5371

Author(s):

Abdelrazek M K Shaltout ◽

Ali G A Abdelkawy ◽

M M Beheary

Keyword(s):

Spectral Lines ◽

Oscillator Strengths ◽

Atomic Data ◽

Dimensional Model ◽

Thermodynamical Equilibrium ◽

Solar Abundance ◽

One Dimensional ◽

Microturbulent Velocity ◽

Non Local ◽

Local Thermodynamical Equilibrium

ABSTRACT Determinations of the solar abundance of praseodymium (Pr) depend critically on the local thermodynamical equilibrium (LTE) and non-local thermodynamical equilibrium (NLTE) techniques beyond the capabilities of a classical one-dimensional model atmosphere. Here, in this analysis, we adopt an atomic model atom of Pr consisting of 105 energy levels and 14 bound–bound transitions of singly ionized praseodymium (Pr ii) and the ground state of the Pr iii continuum limit. We briefly analyse the solar abundance of Pr taking the solar model atmospheres of Holweger & Müller (1974, Solar Physics, 39, 19) with the measured equivalent linewidths and invoking a microturbulent velocity treatment. We succeed in accurately selecting nearby clear sections of the spectrum for 14 spectral lines of Pr ii with the improved atomic data of high-quality oscillator strengths available from the laboratory measurements of several possible sources as well as accurate damping constants successfully determined from the literature. We find a Pr abundance revised to be downwards log ϵPr(NLTE) = 0.75 ± 0.09, which is in good agreement with the meteoritic value (log ϵPr = 0.76 ± 0.03). A comparison of the NLTE abundance corrections with the standard LTE analysis, log ϵPr(LTE) = 0.74 ± 0.08, reveals a positive correction of +0.01 dex, estimated from the selected solar Pr ii lines. The Pr abundance value is clearly superior following the classical one-dimensional model atmospheres of Holweger & Müller, the absolute scales of gf-values, the microturbulent velocity and the adopted equivalent linewidths.

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Growth Mechanism and Optical Properties of Nano and Microstructures of ZnO Obtained by Thermal Oxidation of Zinc Powders at Atmospheric Pressure

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.286.33 ◽

2019 ◽

Vol 286 ◽

pp. 33-39

Author(s):

Carlos Bueno ◽

Abraham Pacio ◽

Edith Osorio ◽

Jose Alberto Alvarado ◽

David Maestre ◽

...

Keyword(s):

Thermal Oxidation ◽

Growth Mechanism ◽

Atmospheric Pressure ◽

Hollow Spheres ◽

Emission Spectra ◽

Green Emission ◽

Bottom Surface ◽

Deep Part ◽

Experimental Conditions ◽

Zinc Powders

ZnO Nano and microstructures were obtained by thermal oxidation using Zn powders as source. To achieve those structures, the Zn powders were annealed at 650°C and 750°C under oxygen environment and atmospheric pressure. SEM results show that these experimental conditions promote the formation of hollow spherical microstructures with nanowires and nano-swords in each sphere. As was observed, the nanostructures start growing from the bottom surface of the spheres unlike those that were reported recently. The EDS results clearly show that those hollow spheres in the deep part make a compound with Zn and the top surface is mainly composed of ZnO. CL emission spectra show a main green emission that belongs to the sphere’s bottom surface; this emission is correlated to the existing defects that are presented. These results could allow the prediction of a possible growth mechanism under specific conditions.

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Fabrication and Properties of Pr3+-Doped Lithium Gadolinium Borate Glasses

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.707.131 ◽

2016 ◽

Vol 707 ◽

pp. 131-134

Author(s):

Kitipun Boonin ◽

Warawut Sa-Ardsin ◽

Jakrapong Kaewkhao

Keyword(s):

Luminescence Intensity ◽

Atmospheric Pressure ◽

Emission Spectra ◽

Xenon Lamp ◽

Borate Glasses ◽

Melt Quenching ◽

Absorption Bands ◽

Color Coordinates ◽

Emission Light

Pr3+-doped Li2O – Gd2O3 – B2O3 glasses (LGBO glass) with the formula 60Li2O:10Gd2O3:(30-x)B2O3:xPrO3 were fabricated using melt quenching technique. The five glass samples with different concentrations of Pr2O3 were prepared under atmospheric pressure. The samples were investigated on their properties: absorption and photoluminescence. All absorption bands are increase with increasing of Pr3+ content. The emission spectra were measured with 446 nm light pumped by xenon lamp. The maximum luminescence intensity was observed at x = 0.50 mol% andthe CIE color coordinates showed the bluish purple emission light for this concentration.

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