Investigation Of The Mechanism In Collisions Of Partially Stripped Ions With Helium Atom

The competition of various reaction channels and the cross section ratios of the double-to-single ionization of helium induced by C^q+,O^q+(q=1～4)ions were studied both in experiment and in theory.The scattering-ion and recoil-ion coincidence technique is used to identify various reaction channels.The energy of these ions ranges from about 20keV/amu to 500keV/amu.This work was performed on the 2×1.7MV tandem accelerator in Lanzhou University.The main results are:1.The reaction channels in collisions of the partially stripped ions with helium are divided into three processes,which are direct ionization process,target ionization associated with projectile electron capture or loss.These three processes competed each other.2.The target ionization contains single ionization(SI)and double ionization (DI).The probability of SI process is larger than DI process.The main reaction channels of DI are transfer ionization(TI),direct double ionization(DI)and double ionization associated with projectile one electron loss.The competition of the three reaction channels is depended on the projectile charge state and the energy.3.The cross section ratios of double-to-single ionization of different processes has the relationship R(TI/SC)＞R(SLDI/SLSI)＞R(DI/SI).The experimental results indicated that the value of R₂₁increase rapidly above 20keV/amu and when the collision energy is about 200keV/amu or 300keV/amu,R₂₁reaches the maximum. Then R₂₁decreases slowly at higher energy.4.A simple model based on Bohr's classical over the barrier model is presented to estimate the cross section ratios of double-to-single ionization.The comparison between the different experimental values and the theoretical calculation shows a qualitative agreement.