The Development Of Inelastic X-Ray Scattering Spectrometer And The Study Of Dynamic Parameters Of CO And CO₂

The study concerning the dynamic parameters of atoms and molecules has always been one of the most important frontier researches in atomic and molecular physics.The dynamic parameters are closely related to the electronic structures of atoms and molecules,such as the initial and final wave functions of atoms and molecules.There-fore,high-precision dynamic parameters will not only deepen our understanding of the electronic structures of atoms and molecules,but also test theoretical modes and cal-culational results rigorously.In this dissertation,we report the development of the first non-resonant inelastic X-ray scattering spectrometer in China based on BL15U1 at Shanghai Synchrotron Radiation Facility.In addition,we have completed the studies concerning the valence-shell excitations of carbon monoxide and carbon dioxide with high-resolution inelastic X-ray scattering method.The achievements and innovations in this dissertation are listed below:(1)We completed the development of the first non-resonant inelastic X-ray scat-tering spectrometer in China,which is installed at BL15U1 Shanghai Synchrotron Ra-diation Facility.The spectrometer works in the 0 a.u.<q~2<15 a.u.momentum transfer squared region with an energy resolution of 1.3 eV and mainly focuses on the studies of dynamic parameters;(2)Using the non-resonant inelastic x-ray scattering with a high resolution of 70 meV,inelastic squared form factors of molecular carbon monoxide have been deter-mined from the ground state X~1?~? to the vibronic states of A~1? and B~1?~+.It is found that for the excitations of A~1?(v'=0—6)the first Born approximation is reached in the region of 0 a.u.<q~2<0.7 a.u.at an impact electron energy of 1.5 keV,while for B~1?~?(v'= 0)the first Bon approximation does not hold except in the region 0 a.u.<q~2<0.15 a.u.;(3)A comparative study of low-lying valence electronic states of carbon dioxide by high-resolution inelastic X-ray and electron scattering have been reported.It is found that the recent calculations taking the vibronic effects into consideration satisfactorily reproduce the inelastic squared form factor profile for the~1?_u~+ transition at about 11.05 eV and the generalized oscillator strength profile for the 9 eV feature.However,the vibronic effects seem to play no role in the ~1?u transition at about 11.40 eV.Further-more,the controversy concerning the designations of electronic states around 11 eV is solved by assigning the two peaks centered at 10.98 eV and 11.05 eV to the vibrational progressionl?_n~+' andl?_n~+',and the peak centered at 11.16 eV to the forbidden transition 2~1 ?_u,based on the electron energy loss spectroscopy results.