Spectral absorption coefficients of carbon, nitrogen and oxygen atoms

Wilson, K. H.; Nicolet, W. E.

doi:10.1016/0022-4073(67)90005-2

Cited by 87 publications

(17 citation statements)

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“…Note that for a specific electronic state bf is only a function of wavelength. Finally, the bound-free absorption coefficient for each energy level is obtained by the bound-free cross section multiplied by the electronic state population as bf X l i1 bf ;i N i (12) where l stands for the number of electronic states modeled in the NEQAIR database. For atomic O and N, there are l 15 out of the total 19 states and 14 out of 22, respectively.…”

Section: A Basic Relations Of Radiation By Atomic Speciesmentioning

confidence: 99%

Advanced Radiation Calculations of Hypersonic Reentry Flows Using Efficient Databasing Schemes

Sohn

Bansal

Levin

et al. 2010

Journal of Thermophysics and Heat Transfer

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Efficient schemes for databasing emission and absorption coefficients are developed to model radiation from hypersonic nonequilibrium flows. For bound-bound transitions, spectral information including the line-center wavelength and emission and absorption coefficients is stored for typical air plasma species. Since the flow is nonequilibrium, a rate equation approach including both collisional and radiatively induced transitions is used to calculate the electronic state populations, assuming quasi steady state. The general Voigt line-shape function is assumed for modeling the line-broadening. The accuracy and efficiency of the databasing scheme was examined by comparing results of the databasing scheme with those of NEQAIR for the Stardust flowfield. An accuracy of approximately 1% was achieved with an efficiency about three times faster than the NEQAIR code. Nomenclature A = Einstein coefficient for spontaneous emission, s 1 Ac; i = Einstein coefficient for spontaneous emission from continuum state to state i, cm 3 s 1 Ai; c = Einstein coefficient for photoionization from state i to continuum state, s 1 Ai; j = Einstein coefficient for spontaneous emission from state i to state j, s 1 a 0 = Bohr radius, 5:29167 10 9 cm B = Einstein coefficient for stimulated emission and absorption, cm 3 -m=J-s B V U = rotational constant, cm 1 b = exponent C, D = vector assembled by excitation rate coefficients of atom C m , D m = vector assembled by excitation and dissociation rate coefficients of molecule c = speed of light, 2:9979 10 10 cm s 1 D w = Doppler line half-width, cm d = parameter in the Voigt width [Eq. (34)] d ff = correction factor for free-free radiation E i = electronic term energy for atomic level i, cm 1 E k = kinetic energy of free electron, cm 1 E emis = total emission energy, W=cm 3 E 1 = ionization energy of an atom, cm 1 e = electron charge, 4:8030 10 10 statC F = rotational term energy for a molecule, cm 1 F i = assembled collisional and radiative coefficient of electronic state i G = vibrational term energy for a molecule, cm 1 GF = Gaunt factor for bound-free radiation G i = assembled collisional and radiative coefficient of electronic state i g = degeneracy H = data points of electron number density and electron temperature h = Planck's constant, 6:6262 10 34 Js J = rotational quantum number j = data point index Kc; i = recombination rate coefficient of collisional transition from continuum state to state i, cm 6 s 1 Ki; c = excitation rate coefficient of collisional transition from state i to continuum state, cm 3 s 1 K Wi = heavy-particle-induced recombination rate coefficient, cm 3 s 1 K W i; j = heavy-particle-induced molecular excitation rate coefficient from state i to state j, cm 3 s 1 K e i; j = excitation rate coefficient of collisional transition from state i to state j by electron impact, cm 3 s 1 K e ci = electron-induced recombination rate coefficient, cm 3 s 1 k = Boltzmann's constant, 1:3806 10 23 JK 1 l = number of electronic states for bound-free transition l m = number of electroni...

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Section: A Basic Relations Of Radiation By Atomic Speciesmentioning

confidence: 99%

Advanced Radiation Calculations of Hypersonic Reentry Flows Using Efficient Databasing Schemes

Sohn

Bansal

Levin

et al. 2010

Journal of Thermophysics and Heat Transfer

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“…For atomic carbon and hydrogen, the oscillator strengths and electronic levels from NIST are applied. In addition, the Stark broadening widths from Griem 59 and Wilson and Nicolet 60 are used for carbon, while for hydrogen, the line shapes and broadening parameters presented by Sutton 61 are applied. The photoionization cross-sections for carbon and hydrogen are obtained by curve-fitting the detailed TOPbase 50 cross-sections.…”

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

The Influence of Ablation on Radiative Heating for Earth Entry

Johnston

Gnoffo

Sutton

2008

40th Thermophysics Conference

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Using the coupled ablation and radiation capability recently included in the LAURA flowfield solver, this paper investigates the influence of ablation on the shock-layer radiative heating for Earth entry. The extension of the HARA radiation model, which provides the radiation predictions in LAURA, to treat a gas consisting of the elements C, H, O, and N is discussed. It is shown that the absorption coefficient of air is increased with the introduction of the C and H elements. A simplified shock layer model is studied to show the impact of temperature, as well as the abundance of C and H, on the net absorption or emission from an ablation contaminated boundary layer. It is found that the ablation species reduce the radiative flux in the vacuum ultraviolet, through increased absorption, for all temperatures. However, in the infrared region of the spectrum, the ablation species increase the radiative flux, through strong emission, for temperatures above 3,000 K. Thus, depending on the temperature and abundance of ablation species, the contaminated boundary layer may either provide a net increase or decrease in the radiative flux reaching the wall. To assess the validity of the coupled ablation and radiation LAURA analysis, a previously analyzed Mars-return case (15.24 km/s), which contains significant ablation and radiation coupling, is studied. Exceptional agreement with previous viscous shock-layer results is obtained. A 40% decrease in the radiative flux is predicted for ablation rates equal to 20% of the free-stream mass flux. The Apollo 4 peak-heating case (10.24 km/s) is also studied. For ablation rates up to 3.4% of the free-stream mass flux, the radiative heating is reduced by up to 19%, while the convective heating is reduced by up to 87%. Good agreement with the Apollo 4 radiometer data is obtained by considering absorption in the radiometer cavity. For both the Mars return and the Apollo 4 cases, coupled radiation alone is found to reduce the radiative heating by 30 -60% and the convective heating by less than 5%. = thickness of the constant-property layers defined in Fig. 3, with i = 1 or 2 (cm) h = absorption coefficient (cm -1 ) = blowing reduction parameter = trasmissivity defined in Eq. (2) Subscripts h = indicates a spectral dependence in terms of eV Superscripts abl = refers to ablation species, meaning species containing any C or H atoms air = refers to air species, meaning species containing no C or H atoms Abbreviations eV = electron volts; the frequency in eV, labeled h , is equal to 1.24x10 -4 / c IR = infrared; refers here to the spectral region below 6 eV NIST = National Institute of Standards and Technology OP = Opacity Project VUV = vacuum ultraviolet; refers to the spectral region above 6 eV

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“…Finally, it should be mentioned that the W and d values from [19,20] are much higher than other data, so they are not included in our discussion.…”

Section: Resultsmentioning

confidence: 99%

The C I 247.8561 nm Resonance Line Stark Broadening Parameters

Djeniže

Srećković

Bukvić

2006

Zeitschrift Für Naturforschung A

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The Stark width (W ) and shift (d) of the neutral carbon (C I) 247.8561 nm resonance spectral line in the 2p 2 1 S 0 − 2p3s 1 P o 1 transition have been measured at 17,600 K electron temperature and 1.08 · 10 23 m −3 electron density in an oxygen-carbon plasma created in an optically thin, linear, lowpressure, pulsed arc discharge. They represent the first experimental results obtained at an electron temperature higher than 14,000 K. We have found a symmetrical line profile, generated dominantly by electrons as perturbers. Our W and d values have been compared to the existing experimental and theoretical data. Good agreement was found between the results calculated by a semiclassical approximation and our data, particulary in the case of the Stark shift.

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Spectral absorption coefficients of carbon, nitrogen and oxygen atoms

Cited by 87 publications

References 5 publications

Advanced Radiation Calculations of Hypersonic Reentry Flows Using Efficient Databasing Schemes

Advanced Radiation Calculations of Hypersonic Reentry Flows Using Efficient Databasing Schemes

The Influence of Ablation on Radiative Heating for Earth Entry

The C I 247.8561 nm Resonance Line Stark Broadening Parameters

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