Determination Of Oscillator Strengths Based On Electron Collision Method And Photoabsorption Method

The oscillator strength represents the transition probability between two energy levels of atoms and molecules,which is the basic physical quantity in the atomic and molecular physics,so it is extremely important to determine the oscillator strength ac-curately from both theoretical and experimental viewpoints.Commonly,the accuracy of the measured oscillator strengths is about 10%.Our laboratory has long committed ourselves to improving the measurement accuracy of the oscillator strength.The high-resolution fast-electron energy loss spectrometer which is devoted to the determination of oscillator strength was built in our laboratory.Furthermore,the relative flow tech-nique is adopted to establish an unified normalization standard.Recently,we proposed a dipole(?,?)method for the determination of the optical oscillator strength based on X-ray scattering technique.In addition,we also attempt to develop the photoabsorption method for determination of the optical oscillator strength.This thesis studies the oscillator strength based on electron collision method and photoabsorption method,and it is divided into two parts.The first part studied the gen-eralized oscillator strengths of a"1?g+(u' = 0)and a"1?g+(v' = 1)+ b1?u(v'= 0)of molecular nitrogen at a high incident electron energy of 1500 eV and a high energy resolution of 70 meV with the aid of the relative flow technique.It is observed that,the present results are apparently different from the X-ray scattering ones in the large momentum transfer region,which indicates that for a"1?g+(v'= 0,1)the first Born approximation is not satisfied at the incident electron energy E0=1500eV in the large momentum transfer region.The agreement of the present results with the X-ray scatter-ing ones for a"?g+(v'=1)+ b1?u(v'=0)in K2<2 a.u.indicates that the first Born approximation is satisfied at the incident electron energy E0=1500eV for b1?u(v'= 0).In the second part,we studied the photoabsorption method deeply for determination of the optical oscillator strength from both theoretical and experimental viewpoints.What's more,in order to overcome difficulties of line saturation effect with the conven-tional photoabsorption method,we proposed a double fluorescence method.Based on our detailed and rigorous derivations,in principle this new method is not limited by the line saturation effect.