Investigation Of The Dynamic Parameters Of Ar,SO₂ And H₂

It is a long-term goal to reveal the basic constitutions and their general working law of the unpredictable world.Atoms and molecules,whose microscopic characteristics determine different macroscopic behaviors of matter,are basic components of the colorful universe.The energy levels and dynamic parameters of atomic and molecular excitations and ionizations are related to the electron correlation effect and configuration interaction.Therefore,the study of accurate dynamic parameters and wave functions is helpful to reveal the structures of matter and understand the related physical effect.In addition,atomic or molecular excitations,ionizations and dissociations are universal phenomena in celestial body,nuclear fusion,plasma,combustion and etc.Therefore,the energy levels and dynamic parameters of atoms and molecules have extensively application in astrophysics,environmental sciences,plasma physics and power source and etc.In this dissertation,the dynamic parameters of Ar,SO2 and H2 were studied by the high-resolution electron energy-loss spectrometer.Meanwhile,based on the third generation synchrotron radiation and ambient-pressure X-ray photoelectron spectroscopy,absolute photoionization cross sections of the subshells of argon are investigated at the photon energies of 100-1500 eV and the momentum distribution of photoelectrons are explored tentatively.The detailed content includes:1.The generalized oscillator strengths,optical oscillator strengths and integral cross sections of A+B、C、E、F、G and H states of the valence-shell excitations of SO2 have been determined at an incident energies of 1500 eV and an energy resolution of 70 meV.It is found that the first Born approximation is not satisfied at the impact electron energies less than 200 eV.The optical oscillator strengths obtained by extrapolating the generalized oscillator strengths to the zero squared momentum transfer are in good agreement with the dipole(e,e)and photoabsorption ones.The integral cross sections determined with the BE-scaling method are coincident with the previous results within the experimeal error,while the calculated ones of A+B and C bands obviously deviate from the experimental results;2.The Fano profile parameters(the q factor,the ratio parameter ρ2,the related continuum fa,the integral GOS f and the resonance strength S)and their momentum transfer dependence behaviors of 3s3p6ns(n=4,5),3s3p6np(n=4,5)and 3s3p63d autoionizations of Ar have been measured at the incident energy of 1500 eV and the energy resolution of 80 meV.The profile parameters in a Rydberg series exhibit similar K2 dependence,and for a Rydberg series,the q and fa are same for different principal quantum number n while the f and S decrease with n.Moreover,the typical dipole-allowed or dipole-forbidden K2-dependence behaviors of the Fano profile parameters can be used to elucidate the properties of electric transition multipolarities;3.The elastic scattering experiment in a large squared momentum transfer region of H2 has been performed at the incident electron energies of 400-1500 eV and the scattering angle of 82.4°.It is found that the electron do interact with a single atom at large momentum transfers,and the interference fringes of H2 disappear.These results are consistent with the quantum theoretical prediction,i.e.,"if the slit through which an electron passes can be distinguished in the double slit interference experiment,the interference fringes will disappear".The experimental results cannot be described by the independent atom approximation theory,so we calculate the energy and scattering intensity of H2 by the recoil-induced vib-rotational excitations theory.It is found that this theory can describe the peak profile of H2,and the vibration effect does smear out the interference fringes.In addition,the vib-rotational energy and translational energy of H2 also conform to the energy distribution in this theory.It is a reasonable model to regard the electron scattering process with large momentum transfer as "the incident electron interacts with an atom,and atomic recoil energy can induce vibrational-rotational excitations of a molecule";4.The absolute differential ionization cross sections of 3s and 3p electrons of Ar at the incident photon energies of 100-1500 eV have been determined by the relative flow technique based on ambient-pressure X-ray photoelectron spectrometer,and then the momentum distributions of orbital electrons have been explored.The present differential ionization cross sections of 3s electron are in good agreement with the theoretical results.The trend of ionization cross section of 3p electron with the incident photon energy is consistent with the theoretical results,while its absolute values are higher than the theoretical ones.The ratios of momentum distribution of Ar 3p and 3s electrons are inconsistent with the calculations,it may be due to that for the present experiment the plane wave approximation of the photoelectron is not satisfied.