Elastic collisions and rotational excitation in positron scattering from<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>molecules

Gianturco, F. A.; Paioletti, P.

doi:10.1103/physreva.55.3491

Cited by 19 publications

(7 citation statements)

References 42 publications

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“…For e 1 scattering, the static interaction is repulsive and the correlation-polarization interaction is attractive, but no exchange interaction exists. Hence, the repulsive static and attractive polarization cancel out, resulting in the smaller interaction on scattering at low-to-intermediate scattering energies, as we have witnessed in the total cross section [3]. It is important, and also our present aim, to examine how these interaction potentials contribute to specific modes in vibrational excitation processes.…”

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confidence: 83%

Mode Dependence in Vibrational Excitation of aCO2Molecule by Electron and Positron Impacts

et al. 1998

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We have found theoretically, for the first time, that vibrational excitations of a CO 2 molecule by electron ͑e 2 ͒ and positron ͑e 1 ͒ impacts are strongly dependent on the charge of the projectile at impact energy below 6 eV. For the symmetric-stretching mode, the excitation cross section of e 2 impact is larger by 2 to 3 orders of magnitude than that of e 1 impact, while for bending and asymmetric-stretching modes the magnitude of both cross sections for e 2 and e 1 impacts is nearly comparable. These results are qualitatively confirmed experimentally, and are interpreted as the difference of interactions and incident e 2 or e 1 wave functions. [S0031-9007(98)05939-0] PACS numbers: 34.80. Gs, A comparative study of electron ͑e 2 ͒ and positron ͑e 1 ͒ scattering from atoms, molecules, and condensed matter is known to provide a fundamental knowledge of underlying physics for electronic structure and scattering dynamics, and hence, is important for atomic physics, condensed matter physics, and nuclear physics [1]. In addition, this knowledge helps in understanding physics for other collision processes which involve different types of exotic particles. Total cross sections by e 1 impact on atoms and molecules are known to give smaller values than those for e 2 impact below about 100 eV to a few eV region, and this feature has been interpreted as a result of cancellation of static and polarization potentials for e 1 impact while these potentials are added up, along with the additional exchange interaction for e 2 impact, thus causing the stronger interaction. For specific inelastic processes, unfortunately, very few systematic studies by e 1 impact have been performed for gaseous targets, and a detailed comparative study between e 2 and e 1 impact is virtually nonexistent except for some preliminary investigation of experimental results for raregas atoms and simple molecules [2]. Only recently, Gianturco and colleagues [3(a)] have carried out a careful study on e 1 scattering from CO 2 molecule for elastic as well as vibrational excitation processes for the symmetric stretching mode, and have compared it with their previous study [3(b)] for e 2 scattering in order to shed some light on the coupling mechanism.Earlier in our study [4], we have observed that the total cross section for CO 2 for e 2 impact is indeed larger by 40% than that for e 1 impact below 100 eV or so, and continues to be so until the impact energy reaches down to 3 eV. Below 3 eV, however, the magnitude of the cross section is found to reverse, i.e., the total cross section for e 1 impact becomes larger by 25%, although it reverses again at much lower energy around 0.5 eV. At the time, we speculated a possible cause for this phenomena as being due to anomalously large cross sections for either rotational or vibrational excitation, or both for e 1 scattering. An exploratory study for rotational excitations by both projectiles was reported some time ago by Takayanagi and Inokuti [5] based on the Born approximation, who showed that for a molecule wi...

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confidence: 83%

Mode Dependence in Vibrational Excitation of aCO2Molecule by Electron and Positron Impacts

et al. 1998

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“…Numerous approaches were proposed in the past, based on modifications of the polarization potential [45], deriving the short-range interaction from electronic densities etc. [46], or expanding the scattering amplitude at low energies [43]. In the present approach we express V S (r) in terms of some boundary conditions imposed on the wave function at r → 0, while the effects resulting from the finite range of V s (r) are included explicitly in the framework of the modified effective-range theory.…”

Section: Scattering Of a Charged Particle On A Molecule And The Quant...mentioning

confidence: 99%

Shape resonances in modified effective range theory for electron-molecule collisions

Idziaszek,

Karwasz

2007

Preprint

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We develop a simple model of shape resonances in electron-molecule collisions that is based on the modified effective-range expansion and analytical solutions of the Schrödinger equation for the longrange part of the interaction potential. We apply our model to electron scattering on N2 and CO2. The parameters of the effective-range expansion (i.e. the scattering length and the effective range) are determined from experimental, integral elastic cross sections in the 0.1 -1.0 eV energy range. For both molecular targets our treatment predicts shape resonances that appear slightly higher than experimentally known resonances in total cross sections. Agreement with the experiment can be improved by assuming the position of the resonance in a given partial wave. Influence of quadrupole potential on resonances is also discussed: it can be disregarded for N2 but gets significant for CO2.In conclusion, our model developed within the effective range formalism reproduces well both the very low-energy behavior of the integral cross section as well as the presence of resonances in the few eV range.

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“…Numerous approaches were proposed in the past, based on modifications of the polarization potential [3], deriving the short-range interaction from electronic densities etc. [34], or expanding the scattering amplitude at low energies [33]. In the present approach we express V S (r) in terms of some boundary conditions imposed on the wave function at r → 0, while the effects resulting from the finite range of V S (r) are included explicitly in the framework of the modified effective-range theory.…”

Section: Introductionmentioning

confidence: 99%

“…Combining ( 9), ( 10), (34), (35) one can easily obtain the low-energy expansion of the phase shifts [11]…”

Section: Introductionmentioning

confidence: 99%

Modified effective-range theory for low energy ${\sf e}$ -N2 scattering

Idziaszek

Karwasz²

2009

Eur. Phys. J. D

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We analyze the low-energy e-N2 collisions within the framework of the Modified-Effective Range Theory (MERT) for the long-range potentials, developed by O'Malley, Spruch and Rosenberg [Journal of Math. Phys. 2, 491 (1961)]. In comparison to the traditional MERT we do not expand the total crosssection in the series of the incident momentum k, but instead we apply the exact analytical solutions of the Schrödinger equation for the long-range polarization potential, as proposed in the original formulation of O'Malley et al.. This extends the applicability of MERT up to few eV regime, as we confirm using some simplified model potential of the electron-molecule interaction. The parameters of the effective-range expansion (i.e. the scattering length and the effective range) are determined from experimental, integral elastic cross sections in the 0.1 -1.0 eV energy range by fitting procedure. Surprisingly, our treatment predicts a shape resonance that appears slightly higher than experimentally well known resonance in the total cross section. Agreement with the experimentally observed shape-resonance can be improved by assuming the position of the resonance in a given partial wave. Influence of the quadrupole potential on resonances is also discussed: we show that it can be disregarded for N2. In conclusion, the modified-effective range formalism treating the long-range part of the potential in an exact way, reproduces well both the very low-energy behavior of the integral cross section as well as the presence of resonances in the few eV range.

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Elastic collisions and rotational excitation in positron scattering fromCO2molecules

Cited by 19 publications

References 42 publications

Mode Dependence in Vibrational Excitation of aCO2Molecule by Electron and Positron Impacts

Mode Dependence in Vibrational Excitation of aCO2Molecule by Electron and Positron Impacts

Shape resonances in modified effective range theory for electron-molecule collisions

Modified effective-range theory for low energy ${\sf e}$ -N2 scattering

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