Binary-encounter-dipole model for electron-impact ionization

Kim, Yong-Ki; Rudd, M. E.

doi:10.1103/physreva.50.3954

Cited by 892 publications

(709 citation statements)

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“…In Fig. 6 we include the calculation of the total ionization cross section using the binary Born-Bethe (BEB) method [53,54]. The present results using the BEB model are in excellent agreement with the measurements of Hudson et al [55].…”

Section: Resultssupporting

confidence: 78%

Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

Vinodkumar¹,

Limbachiya²,

Barot³

et al. 2013

Phys. Rev. A

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Theoretical rotationally elastic total cross sections for electron scattering from methanol over the incident energy range 0.1-2000 eV are presented. The computation of such cross sections for methanol is reported over such an extended energy range. We have employed two distinct formalisms to compute the cross sections across this energy range; between 0.1 eV and the ionization threshold of the target we have used the ab initio R-matrix method, while at higher energies the spherical complex optical potential method is invoked. The results from both formalisms match quite well at energies where they overlap and hence imply that they are consistent with each other. These total cross-section results are also in very good agreement with available experimental data and earlier theoretical data. The composite methodology employed here is well established and can be used to predict cross sections for other targets where data is scarce or not available.

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Section: Resultssupporting

confidence: 78%

Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

Vinodkumar¹,

Limbachiya²,

Barot³

et al. 2013

Phys. Rev. A

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“…The absolute cross sections for electron-impact ionization of H 2 measured by Straub et al (1996) in the energy range E e = 17 eV to E e = 1 keV represent the currently recommended experimental values (Lindsay & Mangan 2003). Analytic expressions and fitting formulae for the ionization cross section have been derived by Rudd (1991), Kim & Rudd (1994) and Liu & Shemansky (2004). Here we adopt the semi-empirical model by Rudd (1991) that gives an analytical expression valid up to relativistic velocities based on the theoretical results of Mott (1930),…”

Section: Ionization Of H 2 By Proton Impactmentioning

confidence: 99%

Cosmic-ray ionization of molecular clouds

Padovani¹,

Galli²,

Glassgold³

2009

A&A

356

475

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Context. Low-energy cosmic rays are a fundamental source of ionization for molecular clouds, influencing their chemical, thermal, and dynamical evolution. Aims. The purpose of this work is to explore the possibility that a low-energy component of cosmic rays, not directly measurable from the Earth, can account for the discrepancy between the ionization rate measured in diffuse and dense interstellar clouds. Methods. We collected the most recent experimental and theoretical data on the cross sections for the production of H + 2 and He + by electron and proton impact and discuss the available constraints on the cosmic-ray fluxes in the local interstellar medium. Starting from different extrapolations at low energies of the demodulated cosmic-ray proton and electron spectra, we computed the propagated spectra in molecular clouds in the continuous slowing-down approximation taking all the relevant energy loss processes into account. Results. The theoretical value of the cosmic-ray ionization rate as a function of the column density of traversed matter agrees with the observational data only if the flux of either cosmic-ray electrons or of protons increases at low energies. The most successful models are characterized by a significant (or even dominant) contribution of the electron component to the ionization rate, in agreement with previous suggestions. However, the large spread of cosmic-ray ionization rates inferred from chemical models of molecular cloud cores remains to be explained. Conclusions. Available data combined with simple propagation models support the existence of a low-energy component (below ∼100 MeV) of cosmic-ray electrons or protons responsible for the ionization of molecular cloud cores and dense protostellar envelopes.

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“…For hydrogen isotopes we use the doubly-differential cross-sections from [19], which we generalize for n > 1:…”

Section: Radiative Recombinationmentioning

confidence: 99%