Experimental Study On State Selective Charge Transfer Between He²⁺ And He, O⁶⁺ And He/H₂

In the last few decades,charge transfer processes in collisions between ions and atoms/molecules have attracted extensive attention due to the growing demands of the corresponding knowledge in different fields.For instance,the origin of background soft X-ray emission in astrophysics and the diagnosis of fusion plasma physics,etc,have all required deeper information on collision induced processes.Comprehensive understanding of relative phenomena in these fields relies on accurate cross sections of interactions or reactions which is essentially belonging to the so-called quantum few-body problem.From the beginning of the century,the reaction microscope has been proven to be one of the most powerful experimental techniques for studies of collision dynamics.Accurate of momentum determination together with the revolutionary 4πsolid angle collection efficiency of charged particles induced in collision processes guarantee unprecedent precisions in fully differential cross section measurements for the specific reaction channels.In this thesis,state-selective and scattering angular differential cross sections of the charge transfer process in collisions between He²⁺and He in the energy range of 30-125 ke V/u,as well as in collisions of O⁶⁺and He/H₂from 19.5-100 ke V/u have been studied with self-developed reaction microscope.A dedicated non-orthogonal time-of-flight spectrometer has been designed and implemented to the reaction microscope to reduce of the charge saturation induced during the beam diagnostics,meanwhile it can also provide a more homogenous electric field and high-precision momentum resolution up to 0.055 a.u.for the recoil ion measurement can be achieved even with a 6 mm-thick target.Single electron transfer processes in collisions of He²⁺on He,and O⁶⁺on He/H₂were studied accordingly.The state selective and angular differential cross sections for different principal quantum number n and the angular quantum number l are obtained with high precision in which the angular differential cross sections of capture excitation channel,marked by（2,2）,were extracted,for the first time,in collisions between He²⁺and He（Here（2,2）refers to the situation in which one of two electrons of the system is captured to the electronic state of n=2,meanwhile the remaining one is excited to n=2 of the residual ion）.Cross sections of corresponding processes are compared with theoretical results based on the two-active-electron semiclassical asymptotic-state close-coupling（SCASCC）approach.It is found that the theoretical results,in general,agree well with the experimental data.It also shows that for the single electron process,the capture mainly occurs at the small scattering angle regime（<0.4 mrad）.Meanwhile,for the transfer excitation processes,a significant contribution on larger projectile scattering angle（>0.6 mrad）can be concluded for 30 ke V/u collision energy.Such differences are the results of the radial and rotational coupling at the small impact parameters in transfer excitation processes.Furthermore,for different collision energies,the oscillatory structure of the Fraunhofer diffraction can be clearly identified in the angular differential cross-section.For the single-electron transfer process in collisions between O⁶⁺and He/H₂,theoretical results from both two-center atomic orbital close-coupling（TC-AOCC）model and classical trajectory Monte Carlo（CTMC）approach have also shown a good agreement to the experimental data at lower impact energies.However,satisfactory description of are still needed when the electron is captured to higher or lower excited states（n=2,n≥6）.For double-electron transfer processes,no significant dependence of the relative cross sections on the impact energy can be concluded in the range of 37.5-100 ke V/u.