Single ionization of helium by proton impact

<p>"Doubly differential cross sections (DOCS) for single ionization of helium by proton impact at incident energies of 50, 75, 100, and 150 keV have been measured using variable angle ion energy-loss spectroscopy. The cross sections, differential in both projectile scattering angle and projectile energy-loss, were obtained by measuring the number of protons incident on a helium gas target that scattered at a certain angle and lost a specific amount of energy as a result of the collision. Data were accumulated for scattering angles ranging from Oto 2 mrad and energy-loss values between 30 and 120 eV for each incident energy. Cross sections were put on an absolute scale by integrating and normalizing the angular distribution for each energy loss and incident energy to a known cross section which was singly differential in energy loss. The doubly differential cross sections were compared to a plane-wave Born calculation which did not include post collision interaction between the projectile and the outgoing electron, and to a modified Born calculation that included the post collision interaction.</p> <p>The cross sections showed no peak structure in the angular profiles for any values of energy loss. Such peak structures have been predicted for larger incident collision energies (≥300 keV) where only binary collisions between the projectile and a target electron were considered. The position of the peak is strongly dependent on projectile energy loss. It has been concluded from these data that the velocity profile of the target electron and scattering from the nucleus prevented this peak structure from being resolved.</p> <p>A dramatic change in the width of the angular distribution of the measured DDCS's as a function of energy loss is observed at an energy loss corresponding to ejected electrons with the same velocity as the projectile. Above this energy loss, the slope of the width versus energy loss curve is drastically increased. A similar effect is observed in the angular distributions of the plane-wave Born calculation which included the post collision interaction between the projectile and the ejected electron"--Abstract, p. iii</p>

Name thesis:degree_name

Ph. D. in Physics

Grantor

University of Missouri--Rolla

Year dc:date.available

2016

Author dc:creator

• Gaus, Aron D.

• Physics

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/950

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-1952