Date of Award


Degree Name

Doctor of Philosophy




Single and double K-shell vacancies in Li-like ions colliding with neutral helium target have been investigated using high-resolution Auger projectile spectroscopy. Be+, B2+, C3+, and O5+ Li-like ions were produced and accelerated to intermediate-to-high collision velocities where perturbative models are expected to be valid, using the Tandem Van de Graaff accelerator at Western Michigan University. Double-K-shell vacancies in atomic systems or so-called “ hollow ions” can be induced by different mechanism in ion-atom collisions. For intermediate-to-high velocity collisions where the collision time is small, the projectile ion can interact with only one of the target electrons to produce a K-shell vacancy. By subsequent rearrangement of the remaining ion, in which electron correlation plays an important role, the second K-shell electron may be excited or ionized. This process is referred to as TS1 (two-step with one projectile interaction). Additionally, at lower projectile velocities, the projectile may interact with each of the target electrons independently to produce two K-shell vacancies. This process is referred to as TS2 (two-step with two projectile interactions). Plane-Wave Bom Approximation (PWBA) was used to calculate the cross sections of the single-K-shell excited states, and was used to compare with the measured ones. The collision velocity dependence of the cross section for the doubly vacant states was used to help determine the mechanism responsible for the hollow states production in the Li-like ions. Different electron correlation effects were inferred from the spectral features of the formed hollow states. The variation of these effects were also investigated as a function of the collision velocity and the atomic number of the Li-like ion.

Access Setting

Dissertation-Open Access