Ionization Of H And He+ By Electrons And Positrons Colliding At Near-threshold Energies

Ionization cross sections for the four combinations of electrons and positrons on H and He+ have been calculated at energies near the threshold for ionization using the classical trajectory Monte Carlo method. In addition, charge-exchange (positronium formation) cross sections have been calculated for the positron-impact collisions. The ionization cross sections compare well with the predictions of the Wannier and Klar models and experimental observations. Our results indicate that the Wannier-type threshold behavior may extend to higher energies than was previously thought. In addition, we have calculated two of the collision parameters, the angle and the relative separation between the escaping particles, used in the Wannier and Klar models, and find good agreement with the values predicted by these theories. © 1986 The American Physical Society

Electron Loss From Helium Atoms By Collisions With Fully Stripped Ions

Electron-loss cross sections have been calculated for fully stripped ions with charge states +1 to +100 colliding with helium atoms in the energy range 100 1000 kev/amu. The classical-trajectory Monte Carlo method was used along with a model of the helium atom with two active electrons. The reactions studied were single and double ionization, single- and double-electron capture, and electron capture plus ionization. Cross sections for the single-electron-removal reactions agree well with experimental data. Double-electron-removal cross sections are in qualitative agreement with experimental results. The n-level distributions following electron capture show that the electron-capture plus ionization and double electron-capture processes are peaked at a lower n level relative to single-electron capture. © 1988 The American Physical Society

Ion Scattering From State-selected Rydberg Atoms

Classical-trajectory Monte Carlo calculations have been performed for collisions of protons with state-selected hydrogenic Rydberg atoms. The examples investigated were Rydberg atoms in the n=10, l=9 level with ml=0 and 9. The collision velocity range was 0.1 to 1.0 a.u. (2.2x107 to 2.2x108 cm/s). The ionization cross sections were found to be relatively insensitive to changes in the ml levels. However, the charge-transfer cross sections showed considerable enhancement if the Rydberg electron is orientated in a plane which is parallel to the direction of the incident projectile. © 1983 The American Physical Society

Double Electron Transitions In Collisions Between Multiply Charged Ions And Helium Atoms

A semiclassical model for He is applied to the study of multiply charged ions colliding with He at intermediate energies. Single and double-electron capture and ionisation and capture-ionisation reactions are studied for incident-ion charge states q=+1 to +50 at 1 MeV amu-1. For charge states q\u3eor approximately=+10, single electron capture is found to be dominated by a two-electron transition in which one electron is captured and the other is ionised

Calculation Of Electron Capture Cross Sections Of Collisions Of Be ²⁺ On H

Using the perturbed stationary state method, including electron translation factors, the authors have calculated electron capture cross sections for the helium-like ions Be2+ and B3+ incident on ground-state atomic hydrogen. The molecular structure calculation employs pseudo-potentials to represent the inactive K-shell electrons on the incident ions. The calculated cross sections vary rapidly in the 107 cm s-1 velocity range (E approximately 1 keV amu-1). The calculations show preferential transfer to the Be+(2s) and the B2+(2p) product states. The calculations for B3++H are in good agreement with experimental measurements of Cradall et al (1979). In addition, the calculations indicate the importance of including rotational coupling to 2 Pi states when determining state-to-state cross sections

Electron Capture Cross Sections For TiH⁴⁺

Electron capture cross sections have been computed for Ti4++H to Ti3++H+ and Ti3++H+ to Ti4++H, where the reactants were in their ground states. The energy range investigated was 0.1 to 10 keV amu-1. The impact parameter perturbed-stationary-state method incorporating electron translation factors were used to calculate the cross sections. The molecular wavefunctions were generated using the pseudo-potential method. At 1 keV amu-1 ( nu rel=4.4*107 cm s-1), representative electron capture cross sections for the Ti4++H and Ti3++H+ reactions are 2*10-15 cm 2 and 1*10-17 cm2, respectively. An appreciable energy dependence was observed for both cross sections

A New Fossil Hawk from the Oligocene Beds of South Dakota

129-132http://deepblue.lib.umich.edu/bitstream/2027.42/48201/2/ID040.pd

Charge Exchange Processes between Excited Helium and Fully Stripped Ions

We made a classical trajectory Monte Carlo (CTMC) calculation of state selective cross sections for processes between some light ions and excited helium. The results, useful for analysis of spectroscopic data of fusion devices, are in good agreement with theoretical predictions of scaling laws.Comment: LaTex, 8 pages, 4 figures (available on request to the authors), DFPD/94/TH/57, to be published in Phys. Rev.