X Ray Study On The Multiple Ionization Induced By Highly Charged Ions Near The Bohr Velocity

The study of the interaction between highly charged ions(HCI)and matter not only has important significance for basic researches such as atomic physics and ion-atom collision reactive dynamics under extreme conditions,but also has important applications in many fields,such as,biomedicine,material science and new energy technology.Near the Bohr velocity,due to the special energy of the projectile,the collision of ions with the atom to produce the inner shell process is more complicated and can produce special physical phenomenon of multiple ionization of the outer shell.However,due to the limitations of experimental conditions,there are few related research reports.The collision mechanism is not yet clear,and it is inconclusive that the existing model is available to such collisions.The further and systematic researches should be done.The study of this dissertation has been taken on the 320 kV highly charged ions experimental platform in the Institute of Modern Physics,CAS.By measuring and analyzing the x ray emission,the multiple ionization induced by Ar,Xe and I ions with different charge state and 0.9 ~ 1.8 Bohr velocity impacting on various target has been investigated.The effect of different collision parameters as incident energy,initial charge state and target atomic number on the multiple ionization,and the change of x ray emission induced by multiple ionization has been studied systematically.As a comparison,the multiple-ionization by proton was also discussed.This study built the gap of related research and achieved the following results.1.The mechanism is confirmed that HCI forms a multiple ionization state near the Bohr velocity.The multiple ionization state of the projectile,which is different form the initial charge state,is the dual effect of electron capture and ionization.It is almost independent on the kinetic energy and charge state of the incident ion,but is linear with the target atomic number.2.The theoretical model for impact ionization in the near-Bohr velocity energy region is identified.The inner-shell ionization produced by HCI near Bohr velocity can be calculated by BEA model,but must be taken into corrections such as Coulomb deflection and binding energy.The estimation of the x-ray emission cross section needs to consider the fluorescence yield of multiple-ionization.3.It is discovered that the multiple ionization by proton is related to incident energy.It is generally believed that the ionization produced by proton is single ionization,and the x-ray data is standard atomic data.However,in this dissertation,it is found that 75 ~ 250 keV protons can produce multiple ionization of the target atom,and that is closely related to the incident energy.With the incident energy increases,the multiple ionization degree rapidly decreases.4.The proton excitation data for x-ray cross sections of Cd,In and Nd elements was extended to the lower energy region of 75 keV.The new data at energies of 75,100 and 125 keV are added.It enriched the PIXE database and verified the applicability of ECPSSR theory of protons in this experimental energy region.