Low-Energy<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>-Ar Total Scattering Cross Sections: The Ramsauer-Townsend Effect

Golden, D. E.; Bandel, H. W.

doi:10.1103/physrev.149.58

Cited by 106 publications

(28 citation statements)

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“…Following Saba [13] Ferch et al [3] Guskov et al [6] Golden and Bandel [5] Golovanivsky and Kabilan [16] - by an iterative method [14]. Here (2/r)Y, (r) is the screening function, (2/r)X;(r) is the exchange function, and (2/r)I, (r) represents terms arising from interactions between configuration states.…”

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Ab initiocalculation of scattering length and cross section at very low energies for electron-argon scattering

Saha

1993

Phys. Rev. A

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The scattering length for electron-argon scattering is calculated very accurately by an ab initio method with wave functions computed exactly at zero energy. The multiconfigurationHartree-Fock method, which takes into account the effects of target polarization and electron correlation through the configuration-interaction procedure, is used for the calculation. The differential, total, and momentumtransfer cross sections are also calculated for very low energies ranging from 0 -1 eV. The present result for the scattering length is found to be in excellent agreement with the experimental results of Buckman and Lohmann [J. Phys. B 19, 2547 (1986)] and Haddad and O' Malley [Aust. J. Phys. 35, 35 (1982)]. PACS number(s): 34.80.8mAt thermal energies, the total, differential, and momentum-transfer cross sections for electron-atom collisions are determined in magnitude and shape primarily by the scattering length. At extremely low energy, extrapolation of the experimental data is difficult and cannot be regarded as reliable. As a result, extremely accurate theoretical calculations are needed to obtain correct cross sections at thermal energies. However, the calculations are made more difficult by the large electron correlations and dynamical polarizations at zero and very low energies. In general, the scattering length is determined by computing phase shifts at lower energies with reasonable accuracy and then extrapolating (tan5o/k) to zero energy. But this does not always guarantee the accuracy of the result. There have been a number of experimental measurements [1 -6] and a few theoretical calculations [7 -10] on the scattering length and cross sections with argon. The most accurate determination of the scattering length from experimental measurements is due to Buckman and Lohmann [1] and Haddad and O' Malley [2]. There is considerable disagreement existing between different sets of experimental results, between different theoretical calculations, and between theory and experiment. Moreover, there is no accurate ab initio calculation of the scattering length and phase shifts at very low energies for the e +Ar case. Since an ab initio calculation of the wave function exactly at zero energy is very difficult, no reliable data for the scattering length have so far been obtained in this way to verify the experimental results. There is therefore an urgent need to perform an accurate ab initio calculation. Very recently we calculated [11] the scattering length and phase shifts at very low energies for electron-neon scattering using the multiconfiguration Hartree-Fock (MCHF) method [12]. The results were in excellent agreement with the measurements.In the present article we intend to apply the same ab initio method to calculate the scattering length and total and momentum-transfer cross sections for the first time in the ab initio way at very low energies from 0.0 to 1 eV, the extremely difficult region for ab initio calculations.It is well known that at zero and very low energies, the polarization and electron-correlation e...

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“…(4). In the present approximation, the coefficients c; need to be determined, and they are solu- Ferch et al [3] Cxolden and Bandel [5] Cxuskov et al [ Fig. 3 the convergence of the total cross sections with respect to the number of orbitals which represent the dipole polarization is shown as a function of electron energy.…”

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confidence: 99%

Ab initiocalculation of scattering length and cross section at very low energies for electron-argon scattering

Saha

1993

Phys. Rev. A

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“…͑C2͒ to the corresponding experimental data are shown in Table I. The values of the total scattering cross sections for carriers [7][8][9][10]19 considered in this article are presented in the Table I. I as well and provided with the range of the parameter E/N where the values shown in Table I are applicable. The electron ͑or ion͒ current corresponding to the drift velocity v d at the certain radius r from the axis of the probe could be written down by the relation:…”

Section: ͑C2͒mentioning

confidence: 99%

“…Substituting the found values i r (0), ͗v͘, and Te into Eqs. ͑4͒ and ͑16͒ at C d F ϭ0.0132, one can calculate that n*ϭ0.185ϫ10 10 cm Ϫ3 , n/n*ϭ1.314, and consequently, nϭ0.243ϫ10 10 …”

Section: "A…mentioning

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I–V characteristics of the Langmuir probe in flowing afterglow plasmas

Shun’ko

2003

Journal of Applied Physics

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The specific features of the probe I–V characteristics in flowing-afterglow plasmas are studied experimentally and in theory. As it was found at a probe potential equal to the plasma one, V=0, an electron concentration in a probe vicinity (and a probe current) is decreased due to a predominant outflow of the electrons into an electrical circuit of the probe from the probe vicinity. The expression allowing one to reconstruct the undisturbed-by-probe electron concentration from only experimental data is derived. The reconstructed values of the electron concentration enable one to find from the experiments the semiempiric expressions allowing to describe quantitatively the behavior of the probe I–V characteristics at the electron-attracting as well as at the ion-attracting potential, respectively. The expressions found (both for electron-attracting and ion-attracting potential) include the “separating length,” which merely is the Langmuir length with a factor equal to the square root of the electron mass over the ion mass ratio for two-component plasma. The intermediate part of the probe I–V characteristics is discovered for probes operating with afterglow plasmas. This intermediate part is described in terms of the experimental parameter L0 having a dimension of the length (presumably electron-orbital length). The value of the parameter L0 does not depend on plasma parameters to within the ranges of plasma parameter variations for experimentally investigated plasmas as it was found. The experiments were performed with two cylindrical probes of 10 and 25 μm diam and ∼3 mm lengths in the experimentally investigated ranges of the afterglow plasma parameters: 105 cm−3<n<1010 cm−3, 0.017 eV<kT<0.3 eV, and 0.5 Torr⩽p⩽2 Torr of He gas pressure (corresponding to 950 μm⩾λTe⩾240 μm electron mean-free path) with (or without) Ar addition.

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Low‐Energy Electrons in Nonpolar Fluids

Davis

Brown

1975

Advances in Chemical Physics

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Low-Energye−-Ar Total Scattering Cross Sections: The Ramsauer-Townsend Effect

Cited by 106 publications

References 12 publications

Ab initiocalculation of scattering length and cross section at very low energies for electron-argon scattering

Ab initiocalculation of scattering length and cross section at very low energies for electron-argon scattering

I–V characteristics of the Langmuir probe in flowing afterglow plasmas

Low‐Energy Electrons in Nonpolar Fluids

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