Kontinuierliche Spektren

Finkelnburg, Wolfgang; Peters, T.

doi:10.1007/978-3-642-45861-3_2

Cited by 12 publications

(9 citation statements)

References 357 publications

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“…10 is readily assignable (37), since there are no significant splittings due to hyperfine structure (which is smaller in 39 K than in 23 Na, 85 Rb, 87 Rb, and 133 Cs). Note the extremely small rotational splittings, corresponding to the very long-range nature of this state (R e ϭ 28 Å).…”

Section: Iia2 Direct Ionizationmentioning

confidence: 99%

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Photoassociation of Ultracold Atoms: A New Spectroscopic Technique

Stwalley

Wang

1999

Journal of Molecular Spectroscopy

246

164

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Section: Iia2 Direct Ionizationmentioning

confidence: 99%

“…It has long been realized that the absorption of light by colliding atoms results in molecular continua (21)(22)(23). In particular, such spectra at ordinary temperatures are broad and continuous whether the upper electronic state is bound (photoassociation) or free.…”

Section: Ia Photoassociationmentioning

confidence: 99%

Photoassociation of Ultracold Atoms: A New Spectroscopic Technique

Stwalley

Wang

1999

Journal of Molecular Spectroscopy

246

164

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“…(1) (a) H continuum: The first term in the square brackets represents the contribution from the H continuum [13] with high density corrections according to reference [10]. Ne is the electron density (cm- 3 ), T is the tern· perature (K), h. is the wavelength (cm), C2 is the second radiation constant (= 1.43879 cm K), Ei is the ioniza· tion potential of hydrogen, tilli is the lowering of the ionization potential given by tilli = e 2 /pD [10], where PD= [kT/81Te2Ne] 1/2, Yff and Yfb are the free-free and free-bound Gaunt factors respectively [14] averaged over a Maxwellian velocity distribution, and n is the upper state principal quantum number.…”

Section: + G(a T) Nenh+f(a T)npnh+q(a T)n~}x 107 _mentioning

confidence: 99%

“…In order to calculate diE, "IdE, it is defined in terms of the absorption cross section [25]: The calculation is for a pure hydrogen plasma in LTE at I atm with T= 13000 K. [10][11][12][13][14][15] cm-3 • and AEi =O.0772 eV. Curve A represents the continuum calculated with nmln = 2 in eq (1).…”

Section: -%-------------------------------------N-1 Figure 1 a Schemmentioning

confidence: 99%

The calculated continuous emission of a LTE hydrogen plasma

Roberts¹,

Voigt²

1971

J. RES. NATL. BUR. STAN. SECT. A.

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The total continuou s emission coefficient for a L TE hydrogen plasma at one atmosphere is calculated for a temperature range from 8000 to 16000 K and a wavelength range from 400 to 15000 A.Contributions involving the species H, Hi, H-, and H2 , as well as the wings of Stark-broade ned hydroge n lines are included. This calculati on wi ll permit th e radiation e mitted from a laboratory hydroge n plasma to be used as a high intensity spectral radian ce calibration standard_

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“…experimental and theoretical studies of continuum radiation, particularly on polyelectronic atoms and ions for which the hydrogenic approximation yields poor estimates, reference should be made to the review article by Finkelnburg and Peters. 9 Finkelnburg and Peters cite 496 references, many of which correspond to papers published during the period 1937 to 1956, following completion of Finkelnburg's monograph on continuum spectra. lO The latter publication includes reference to 1700 papers appearing up to 1937 and beginning essentially with the classical analysis of Kramers.ll Proper appreciation of this rich historical background will serve to place the present paper in its correct perspective: a simplified prescription of calculating useful data that should be of value to the applied scientist who may content himself with approximate results that can really be improved significantly only at the expense of considerable complication in analytical procedure.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Approximate theoretical calculation of continuum opacities

Penner

Thomas

1964

AIAA Journal

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An approxhnate procedure is described for the theoretical calculation of the spectral absorption coefficient produced by bound-free and free-free transitions in plaslllas containing polyelectronic atollls and ions. Our lllethod of calculation is based on the assulllption that only two ionized species lllake illlportant contributions to the opacity and that these two ionic constituents are present in equal concentrations. The approxilllate forlllulas are shown to yield results that are in good accord with estilllates based on detailed numerical cOlllputations for nitrogen. In trod uctionA PPROXIMATE expressions for the Rosseland and Planck mean free paths associated with the continuum radiation in ionized plasmas have been derived by Menzel and Pekeris 1 and by Pappert and Penner.2 The last named authors followed a procedure described by Raizer. • 4The method of calculation introduced by Raizer 3 • 4 and used by Pappert and Penner 2 differs from that employed in the earlier work of Menzel and Pekeris 1 by including only two representative m times ionized atoms instead of approximating the sum over the ions by an integral. The physical reasons for the use of this approximation may be made plausible by referring to the schematic diagram shown in Fig. 1 where the concentration of m ions (i. e., of m times ionized atoms) is shown as a function of temperature. We note that there will be temperatures Tat which the plasma composition is well described by the presence of two ionic constituents that are present in equal concentration. Since all physical observables are expected to vary continuously with temperature, we expect that the use of the assumption that only two m ions are present in equal concentrations for all values of T must lead to a good prediction of electron concentration at all temperatures. The use of this idea, together with the introduction of several supplementary simplifications due to Raizer, has previously2 been shown to lead to results that agree, within about a factor of 2, with the best available numerical 5 computations for Rosseland and Planck mean free paths. On the other hand, it is known 8 that the errors introduced by neglecting line radiation are of the same magnitude as, or larger than, the previously noted discrepancies resulting from the use of highly simplified computational procedures, particularly at elevated temperatures and low densities. For this reason, it appears justified to avoid the labor involved in obtaining a complete solution to the Saha equation and to utilize again the approximation of two m ions present in equal concentrations. We shall then show that the resulting estimates for the spectral absorption coefficients of nitrogen also agree, well within a factor of 2 over most of the frequency range, with the best available numerical computations.t II. Theoretical ConsiderationsIn the following discussion we shall deviate from the analysis of Pappert and Penner 2 by considering the corrections required through proper introduction of statistical weight factors, which we...

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Kontinuierliche Spektren

Cited by 12 publications

References 357 publications

Photoassociation of Ultracold Atoms: A New Spectroscopic Technique

Photoassociation of Ultracold Atoms: A New Spectroscopic Technique

The calculated continuous emission of a LTE hydrogen plasma

Approximate theoretical calculation of continuum opacities

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