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This paper reports that the ratios of double to single electron loss cross-section (R) of O2+ in collision with Ar and He at the velocity of 1–4ν0 (ν0 is the Bohr velocity) have been obtained by the coincidence technique. The trend of R – V in the experiment indicates that the effective charge varies with injected velocity. The effective charge can be obtained by the n-body classical trajectory Monte Carlo method, which is interpreted by the molecular Coulomb over barrier model.

The ratios of transfer ionization (TI) to single-electron capture (SC) cross sections have been measured for the collisions of partially stripped Cq+ ions (q = 1-4) with He. The collision velocity ranges from 0.7 to 4.4v(0) (v(0) is the Bohr velocity). The projectile-ion and recoil-ion coincidence technique is used to separate the processes of TI and SC. The ratios reach the maximum when the velocity is about 3.7 v(0). This can be explained qualitatively based on the two-step mechanism. The experimental results are also compared with the results calculated using the classical trajectory Monte Carlo (CTMC) method. The CTMC results are in agreement with the experimental data basically. The discrepancies in higher velocity region are interpreted by the effective charge effect.

The multi-electron processes are investigated for 17.9–120 keV/u C1+, 30–323 keV/u C2+, 120–438 keV/u C3+, 287–480 keV/u C4+ incident on a helium target. The cross-section ratios of double electron (DE) process to the total of the single electron (SE) and the double electron process (i.e. SE+DE), the direct double electron (DDI) to the direct single ionization (DSI) as well as the contributions of DDI to DE and of TI to DE are measured using coincidence techniques. The energy and charge state dependences of the measured cross-section ratios are studied and discussed.

In this work, the ionizations involving the charge transfer and single capture processes in low charge state ion-atom collisions in low-to-medium energy region, are investigated by the position sensitive and time-of-flight techniques. For a given charge state of the incoming projectiles, the dependence of the ratio RTS of the transfer ionization to the single capture changing with the projectile velocity is obtained, and the conclusion that the ionized electron in the transfer ionization process comes from the outermost sub-shell of the target atom is confirmed by comparing our theoretical results with the experimental data.

This paper presents the measurement results of absolute cross-sections of ion-atom collision in detail. The pure cross-sections of Nei+(i=1—4) induced by C3+ were investigated using coincidence technique. Comparing our experimental results with those of n-body classical trajectory Monte Carlo method, it is found that the changes of pure cross sections with increasing energy have the same trend in the two cases. The causes of discrepancies between them are discussed. The mechanism of multiple-ionization is analyzed. The highly charged recoil ions come mainly from the Auger effect. The electron-electron interaction comes in to effect as the incident energy increases. The cross-sections of all kinds of reactions can be measured in this way using the same equipment and projectile ions can be various within a wide range of energy.

he cross-section ratios for the double-to-single ionization of He associated with no projectile charge change ( R q , q ), single-electron capture ( R q , q -1 ) and single-electron loss ( R q , q +1 ) were measured using coincidence technique. The coincidences resulted from the signals of recoil ions and scattered projectiles. For a given incoming projectile charge state the double-to-single ionization ratios vary strongly with the outgoing reaction channel. It is found that R q , q R q , q +1 R q , q -1 . For direct ionization, R q , q is nearly independent of the incident projectile charge state. However, for ionization associated with single-electron capture and single-electron loss by the projectile, R q , q -1 and R q , q +1 depend strongly on the incident charge state of the projectile. These ionization ratios are interpreted in terms of theories of the atomic polarization effect and the screening and antiscreening effect of the electrons around the core.