Experiment Study Of Charge Exchange Between Low-energy Argon Ions And Helium Target

Charge exchange processes involving ions in highly charged states have not only contributed to the understanding of quantum few-body problems in Coulomb fields,but also have an important role in laboratory plasma diagnostics,biological irradiation effects,and astrophysics studies.So far,there are few studies on the collision processes associated with Ar⁸⁺ions,and most of these studies are based on spectroscopic techniques,energy-loss spectrometers and electron spectrometers,which make it difficult to obtain comprehensive and reliable information on total cross sections and scattering angles.Therefore,based on the EBIS low-energy high-charge state ion platform and the reaction microscopy imaging spectrometer at the Institute of Modern Physics,Chinese Academy of Sciences,we investigated the charge exchange processes in Ar⁸⁺-He collisions,including the state-selective cross sections and angular differential cross sections of single-and double-electron exchange,determined the information of the charge exchange states and the collision parameters,and compared the results with various theories.The results of this work show that(1)for the 40 ke V and 120 ke V Ar⁸⁺-He collision systems,the reactions are dominated by single electron capture(SEC).(2)For the 40 ke V and 120 ke V Ar⁸⁺-He collision system,the single electrons are mainly captured to the 4l and 5l states of Ar⁷⁺,and the proportion of the 4l state is significantly larger than that of the 5l state,and the reaction window calculated by MCBM is basically consistent with the experimentally obtained state range of the electrons,i.e.,the Q distribution of the reaction calculated by MCBM well predicts that the electrons are mainly captured to the 4l and 5l energy levels.(3)The experimental results of Ar⁸⁺-He single-electron capture show that the scattering angle distribution has a clear correlation with the electron energy level,and the scattering angle gradually becomes smaller when the energy level of the captured electrons gradually increases from 4p to 5p.In addition,there is also a correlation between the scattering angle and the incident ion energy.When the energy of the incident ion increasing from 40 ke V to 120 ke V,the scattering angle of the incident ion decreases as a whole,and the relationship between them can be explained by the classical two-body collision model.(4)When the scattering angle distribution of the single electron capture of 120 ke V Ar⁸⁺-He collision was investigated,it is found that the scattering angle distribution shows a clear oscillation structure when the electrons are captured to the 4s state.The scattering angle oscillations in this experiment can be successfully explained using the optical theory of Fraunhofer diffraction and the radius of the circular hole obtained from the MCLZ and MCBM models,i.e.,the collision of the low-energy incident ion with the target atom will form a quasi-molecule,and when the spacing between the two nuclei tends to infinity after the collision,the interference between the parity orbitals of the quasi-molecule leads to the possibility of the same atomic state,which eventually leads to the emergence of oscillations.