Jun Forest

Date of Award


Degree Name

Master of Arts



First Advisor

Dr. John A. Tanis

Second Advisor

Dr. Emanual Kamber

Third Advisor

Dr. Alvin Rosenthal

Access Setting

Masters Thesis-Open Access


Ionization of helium target atoms by He+ projectiles colliding with helium at energies of 0.125 to 3.0 MeV/u is investigated. Cross sections for single and double ionization, and ratios o f double-to-single ionization are determined for each outgoing projectile charge state, and are compared to previous studies. For the lowest energies investigated, the ratios are consistent with the two-step mechanism in which the projectile interacts separately with each target electron. At the highest energies, the ratios reach nearly constant values indicating approach to the high velocity limit. At these high energies, however, the ratios are all higher than the value predicted by the empirical equation of Knudsen et al. (1984). Furthermore, the constant ratios in the high velocity limit are strongly dependent on the outgoing projectile charge state indicating different amount of electron correlation being responsible for double ionization associated with projectile capture, loss, or no charge change, respectively.