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Welsh, Leland M.; Berkner, K.H.; Kaplan, S.N.; Pyle, Robert V.

doi:10.1103/physrev.158.85

Cited by 148 publications

(51 citation statements)

References 31 publications

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“…However, the scaling factor has a value of 1.25, close to but larger than the value of 1.202 [70]. Experiments: squares, Schryber [61]; circles, Welsh et al [65]; triangles, Williams [64]. [77].…”

Section: High Energy Collision (E > 100 Kev/u)mentioning

confidence: 96%

“…Theory: black dashed line, eikonal molecular method, reaction (1); red dashed line, eikonal molecular method, reaction (2); black solid line, eikonal atomic method, reaction (1); red solid line, eikonal atomic method, reaction (2). Experiments: crosses, Berkner et al [60]; squares, Schryber [61]; full diamonds, Schwab et al [62]; full triangles, Shah and Gilbody [63]; inverted triangles, Shah et al [54]; triangles, Williams [64]; full inverted triangles, Stier and Barnett [51]; circles, Welsh et al [65]; diamonds, Rudd et al [52]; full circles, Martin et al [53]; plus signs, Allison [40].…”

Section: High Energy Collision (E > 100 Kev/u)mentioning

confidence: 99%

See 1 more Smart Citation

Charge transfer in proton–helium collisions from low to high energy

Loreau

Ryabchenko

Vaeck

2014

J. Phys. B: At. Mol. Opt. Phys.

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The cross section for charge transfer in proton-helium collisions has been computed in the energy range from 10 eV/u up to 10 MeV/u. Four different methods (full quantal time-independent and time-dependent methods, molecular and atomic basis set semi-classical approaches) valid in different energy regimes have been used to calculate the partial and total cross section for single-electron capture. The results are compared with previous theoretical calculations and experimental measurements and the different theoretical methods used are shown to be complementary for describing the charge transfer reaction. A fit of the cross section, valid for collision energies from 10 eV/u up to 10 MeV/u is presented based on these results.

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Section: High Energy Collision (E > 100 Kev/u)mentioning

confidence: 96%

Section: High Energy Collision (E > 100 Kev/u)mentioning

confidence: 99%

Charge transfer in proton–helium collisions from low to high energy

Loreau

Ryabchenko

Vaeck

2014

J. Phys. B: At. Mol. Opt. Phys.

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“…Experimental data for the ionization cross section: empty circles, Shah & Gilbody (1985). Data for the electron capture cross section: filled circles, Welsh et al (1967); diamonds, Shah & Gilbody (1985). Data for the total ionization cross section: crosses, Pivovar & Levchenko (1967); triangles, Puckett & Martin (1970); squares, DuBois et al (1984).…”

Section: Ionization Of He By Proton Impactmentioning

confidence: 99%

“…The cross section for this charge transfer reaction has been measured by Welsh et al (1967) and Shah & Gilbody (1985). The cross section has a maximum at E p ≈ 25 keV, where it is about one order of magnitude larger than the ionization cross section σ ion p (see Fig.…”

Section: Ionization Of He By Electron Capturementioning

confidence: 99%

Cosmic-ray ionization of molecular clouds

Padovani¹,

Galli²,

Glassgold³

2009

A&A

352

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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“…He also notes that Eq. and atomic hydrogen in gases we give a few of the more comprehensive references: experimental results are contained in reviews by Allison (1958), Allison and Garcia-Munoz (1962), Welsh et al (1967), and in a paper by Toburen et al (1968); theoretical formulations have been presented by Bates and Carroll (1962), Bates (1962), Dalgorno (1964) , Nikolaev (1966) , and Bates and Mapleton (1967).…”

Section: Ivie Theory By Bohr and Lindhardmentioning

confidence: 99%