Experimental Investigations Of Collision Dynamics Of Intermediate Energy He²⁺ Impact On Ar And Co

By employing reaction microscopes, we studied the electron emission mech-anism in intermediate energy ion-atom collisions and the interference effect of particle wave in intermediate energy ion-molecule collisions.In the single-electron capture with simultaneous single ionization (T1I1) processes of 30 keV/u He2+-Ar collisions, it is found that the emitted electrons with kinetic energies (Ee) above 20 eV concentrate mainly in forward direction at small transverse recoil momentum. The characteristic of binary encounter (BE) between the projectile and the target electron is observed in the two-dimensional spectrum of the kinetic energy and the emission angle (0) of the emitted elec-trons, where θ is denned by the directions of the incoming projectile and the emitted electron. As the transverse recoil momentum increase, more and more electrons of Ee> 20 eV emit in the backward directions and the BE characteris-tic gradually vanishes. The same phenomena are also observed in T1I2 and T2I1 processes of the collision system. A classical model starting from the BE scatter-ing is proposed to explain the phenomena and a new binary-encounter formula where the initial velocity and binding energy of the emitted electron are taken into account is derived. At small transverse recoil momentum, the BE electron distributions predicted by the new formula are in good agreement with the ex-perimental results in the two-dimensional spectra, and the distributions of the relative cross sections calculated by the Rutherford scattering formula combined the new formula are also in good agreement with the experimental results for the emitted electrons with Ee> 20 eV. At large transverse recoil momenta, the moving directions of BE electrons are changed by the target nuclei and the BE characteristics vanish in the two-dimensional spectra.In double capture processes of 30,50 and 135 keV/u He2+-CO collisions, all fragments of CO2+ of kinetic energy release (KER) below 15 eV are detected in 4π solid angle, and the experimental resolution is good enough to distinguish dif-ferent molecular states of CO2+. As the velocity of the projectile (vp) increasing, the projectiles tend to capture inner shell electrons of CO, thus CO2+is more likely to populate higher molecular states. In our work, the orientations of molec-ular axises in collisions are determined via measuring C+ and O+ momenta for the dissociations of CO2+ in repulsive states. The orientation effects of molecular axis deriving from the interference of the projectile particle waves from the two atomic centers of CO are observed for the CO2+ dissociations in 3Σ-,1Δ and 3ΠⅡ stats. Comparing with the case of ion collisions on homo-diatomic molecule, the unique asymmetric orientation distributions which are from the difference of the reaction amplitudes at C and O centers are firstly observed.