Investigation On The Electron-impact Rate Coefficients For Rare Gas Atoms

Rare gas discharges are widely used in the fundamental research and industrial applications of low temperature plasmas.In the discharges containing rare gases,the electron-impact process is one of the most important kinetic processes.In particular,the electron-impact excitation or transfer processes from the 1s states of the rare gas atoms are one of the most important production processes for the activity species in discharges.Therefore,the rate coefficients for these electron-impact processes are essential for the investigation on these discharges.However,for these electron-impact processes,their rate coefficients are not available.In this work,we determine the electron-impact rate coefficients from the rare gas atom 1s states by a combination of plasma modeling and diagnostics of key discharge parameters.This is achieved by highlighting relevant electron-impact processes with discharge condition manipulation and accurate measurement of the discharge parameters with diagnostics developed in the laboratory.With the measured data,the rate coefficients can be determined from the rate equation of a certain excited state.With this method,the rate coefficients of the important electron-impact processes from1 s states of argon and krypton are obtained.New findings in this work are as follows:1.A method is proposed to measure the rate coefficients for the important electron-impact processes from 1s states in rare gases discharges.In this method,the afterglow plasmas,where the ground excitation is negligible,are used to highlight the 1s excitation.In addition,different 1s state excitation can be highlighted in several selected discharges.With the accurate diagnostic of the discharge parameters,the electron-impact rate coefficients can be obtained from the population model.This method can be used in determining the rate coefficients of many important electron-impact processes from 1s states of gas atoms.2.The rate coefficients for 58 electron-impact processes of rare atoms(Ar and Kr),where 35 of them are obtained for the first time,are measured by using the proposed method.These rate coefficients will play an important role in the plasma modeling and the optical diagnotics.In addition,these results can be used to test the rate coefficients data obtained by the theoretical calculations.3.New optical methods are proposed to measure the electron temperature and argon metastable state density evolution in low pressure argon pulsed discharges.These methods can be used to obtain the electron temperature and the argon metastable density for many industrial discharges,when other diagnostic methods do not work due to some limitations,such as the strong rf distortion,low ionization rate or the required complicated set-up.