عنوان

Single ionization in highly charged ion-atom collisions at low to intermediate velocities

TLpq304452023

انگلیسی

Single ionization in highly charged ion-atom collisions at low to intermediate velocities

[Thesis]

M. A. Abdallah

C. L. Cocke

Kansas State University

1998

197

Ph.D.

Kansas State University

1998

Single electron ejection from neutral targets (He and Ne) by the impact of low to highly charged ions (p, usd\rm He\sp+,\ Ne\sp+,\ He\sp{2+},\ C\sp{6+},\ O\sp{8+},usd and Ne at low to intermediate impact velocities is studied. A novel technique of electron momentum imaging is implemented. In this technique two-dimensional electron momentum distributions are produced in coincidence with recoil ions and projectile ions. In first generation experiments we studied the ejected electron momentum distributions without analyzing recoil ions momentum. This series of experiments revealed a charge-state dependence and velocity dependence that are contradictory to a dominant saddle point ionization mechanism at intermediate velocities. It showed a possibility of an agreement with a saddle centered distributions for low charge states at low collision velocities. To pursue the problem in more detail, we developed a second generation spectrometer which allowed us to fully determine the recoil ions momentum. This allowed us to determine the collision plane, energy loss (Q-value), and impact parameter for every collision that resulted in a single (target) electron ejection. This series of experiments revealed for the first time very marked structure in electron spectra that were impossible to observe in other experiments. These structures indicate the quasi-molecular nature of the collision process even at velocities comparable to the electron "classical" orbital velocity. For the collisions of p, He and He with He, a usd\piusd-orbital shape of the electron momentum distribution is observed. This indicates the importance of the rotational coupling usd2p\sigma\to2p\piusd in the initial promotion of the ground state electron. This is followed by further promotions to the continuum. This agrees with the "classical" description implied by the saddle-point ionization mechanism picture.

Atoms & subatomic particles

ejected electrons

projectile ions

Pure sciences

recoil ions

C. L. Cocke

M. A. Abdallah

p

[Thesis]

276903

a

Y