Velocity Dependence of the Differential Cross Sections for the Scattering of Atomic Beams of K and Cs by Hg

Morse, F. A.; Bernstein, R. B.

doi:10.1063/1.1733421

Cited by 88 publications

(12 citation statements)

References 10 publications

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“…of the solid angle[34]. The efficiency e's for the Ar atoms and the Na atoms are almost the same within the experi-…”

supporting

confidence: 62%

“…5is the elastic DCS o(8)sin8 in the c.m. frame, which was deduced from the DCS cr(8) in the laboratory system measured at 70~El, b~3 50 eV by taking into account the Jacobian factor for transformation[34]. The open circles are the DCS's deduced from the Na+-ion data measured at 0&92', while the solid circles for EI b =200 and 350 eV at large angles are the DCS's evaluated from the intensity of the Ar atoms at 0&27 with the detection eKciency c of the multiplier.…”

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confidence: 99%

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Excitation mechanisms in moderate-energyNa+-Ar collisions

et al. 1995

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By means of differential energy-transfer measurements, excitation mechanisms in Na -Ar collisions have been studied at laboratory collision energies of 50~Ei, b~1 500 eV. In these experiments, doubly differential cross sections have been measured over nearly the whole angular range in the center-of-mass system by simultaneously detecting both scattered and recoiled particles (Na+, Na, Ar+, and Ar) at lab-

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“…of the solid angle[34]. The efficiency e's for the Ar atoms and the Na atoms are almost the same within the experi-…”

supporting

confidence: 62%

mentioning

confidence: 99%

Excitation mechanisms in moderate-energyNa+-Ar collisions

et al. 1995

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“…frame results in a range of observed axial components in the lab frame, due to scattering through all azimuthal angles. Thus corrections were carried out over the full range of azimuthal angles, using standard transformation equations [12]. In the present case, where the beams intersect at right angles and the electron velocity is greater than 10 times the ion velocity, the resulting correction is small within the angular range studied.…”

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confidence: 99%

Large Angle Elastic Scattering of Electrons from Ar+

1995

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Absolute angular differential cross sections have been experimentally determined for large angle scattering of a free electron by a positive ion for the first time. Data are presented for elastic scattering over the range 120 -170 from Ar+ at 3.3 eV. Interference effects are observed due to the competing short-range and Coulomb interactions.The importance of interference and correlation effects is demonstrated, and the consequent sensitivity of such measurements as a test of theoretical approximations is discussed. PACS numbers: 34.80.Bm, 34.80.KwThe elastic scattering of electrons from neutral atoms has been extensively investigated both experimentally and theoretically.Interference structure is typically evident in the angular differential cross sections (DCS) [1].

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“…It was possible to measure the fractional difference between the cross sections Q3/2 1/2 and Q3/2 3/2 (where the subscripts refer to J and IMTj, respectively); the results were 1.0, 0.8, and 2.0 percent, respectively, for scattering by xenon, argon, and helium [after suitable processing (8) of the data so that the results refer to collisions for which Vr is perpendicular to the polarization axis]. Schlier's (57) theoretical analysis yielded the approximation formula Qj,= Q bJ,/5 (1 + a/6) (14) where Q is the Schiff-approximated cross section for a spherically symmetrical potential.…”

Section: Vj (R 0) = R Bj (Kc) [1 + Ajm () Cos2 0] (13) Where 0 Imentioning

confidence: 99%

Molecular Beam Scattering at Thermal Energies

Bernstein

1964

Science

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The observation of the scattering of molecular beams by gases is as old as the original discovery of the "molecular ray" by Dunoyer (1) in 1911. In the 1920's a number of semiquantitative studies of scattering were carried out (2). These consisted of measurements of the mean free path for molecular beams passing through gases at low pressure. Effective collision cross sections calculated from such mean-freepath data were comparable to, but generally larger than, the so-called "kinetic theory cross sections" based on transport properties (for example, viscosity and diffusion). More accurate and extensive experiments of a similar nature followed (3-5) during the 1930's; it was then recognized that precise measurements of scattering would yield, in a direct way, valuable information on the laws of interaction between the colliding molecules on a microscopic scale, from which the macroscopic gas properties could be calculated with the aid of statistical mechanical procedures.The concept of an effective molecular collision cross section, usually designated Q (or u), has been a useful one. It is defined as Q = vrro, such that the actual collision rate would be reproduced by a calculation of the collision rate assuming the molecules to be hard spheres of diameter ro. In general, molecular-collision cross sections pend upon the incident relative velo( vr; usually Q decreases with increasVr.The cross section may be expres in terms of the attenuation of a mo energetic molecular beam pas, through a "static" target gas of knc density: -= e-Q = e-1/x lo where I/Io is the transmittance, 1 is length of the scattering zone, n is number density of target molecules is the cross section (6), and X = 1/ is the mean free path of the beam n ecules.Usually, Maxwellian velocity di, bution of beam and target gases involved, so the cross sections or m free paths obtained from measurem( of 1/Io by means of Eq. 1 are avera over the velocity distributions (4, 7,The symbol Qeff has been used (8) designate the "effective" cross secti that is, 1Io Qef--f =lIn The true cross section is related to < by a (dimensionless) factor which function of the temperatures of beam source and scattering gas and appropriate velocity distribution fu tions.The angular distribution of the s tering is also of considerable inter Simple considerations suggest that the low-angle scattering is sensitive primarily to the long-range attractive interaction, while the large-angle scattering yields information mainly about the short-range repulsive forces (9). The earliest measurements (10-12) indeed showed the expected strong forward peak in scattered intensity arising from the long-range intermolecular attractive forces.The angular distribution is described in terms of the so-called "differential" scattering cross section, defined as follows (for the simple case of scattering by a spherically symmetrical potential).Let dn12 be the number of collisions occurring per unit time per unit volde-ume between molecules moving with ity relative speed Vr, for which the relative ve...

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Velocity Dependence of the Differential Cross Sections for the Scattering of Atomic Beams of K and Cs by Hg

Cited by 88 publications

References 10 publications

Excitation mechanisms in moderate-energyNa+-Ar collisions

Excitation mechanisms in moderate-energyNa+-Ar collisions

Large Angle Elastic Scattering of Electrons from Ar+

Molecular Beam Scattering at Thermal Energies

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