Studies Of VUV Synchrotron Radiation Photoionization And Dissociative Photoionization Of Some Esters

In this dissertation, we study the photoionization and dissociative photoionization of some esters using synchrotron radiation. With the help of ab initio calculation, we analyze the experimental results and establish the dissociation channels of these esters.In the first chapter, we briefly introduce the history and the characteristics of synchrotron radiation. We present the advantages of synchrotron radiation and its superiority on scientific research. We also describe the application in atomic and molecular science of the synchrotron radiation. And we particularly discuss the interaction between the photon and substance.In the second chapter, an introduction is given about the atomic and molecular physics beamline and endstation of National Synchrotron Radiation Laboratory in the PhaseⅡprojects. Firstly, the experiment setup is introduced. Secondly, the operation principle of the endstation are described. Finally, we briefly introduce the gas filter system of the endstation.In the third chapter, the theoretical methods used in this thesis are briefly presented.In chapter 4, the photoionization and dissociative photoionization of methyl ester have been studied at the photon energy range of 9～15.5 eV. This chapter consist of four parts:1) Firstly, we measure the mass spectra of methyl ester. Then we confirm the main fragment ions of the photoionization dissociation of methyl ester, including m/e = 85(C4H5O2+), 68(C4H4O+), 59(CH3OC=O+), 58(CH2=CHOCH3+), 55(CH2=CHCO+), 42(C3H6+), 27(CH2=CH+) and 15(CH3+).2) secondly, the ionization energy (IE) of the molecule, CH2=CHCOOCH3, and the appearance energies (AEs) of the fragment ions, including m/e = 85(C4H5O2+), 68(C4H4O+), 59(CH3OC=O+), 58(CH2=CHOCH3+), 55(CH2=CHCO+), 42(C3H6+), 27(CH2=CH+) and 15(CH3+), have been measured.3) Thirdly, we calculate the energies of the fragment ions by using the ab initio Gaussian-3 (G3) procedure. The calculated IE of the methyl ester molecule is 10.12 eV, which is in excellent agreement with the experimental result, 10.20±0.03 eV.4) Combined the experimental results with the ab initio calculation, the dissociation channels of the fragment ions C4H5O2+, C4H4O+, CH3OC=O+, CH2=CHOCH3+, CH2=CHCO+, C3H6+, CH2=CH+ and CH3+ are analyzed. The corresponding dissociation energies are also obtained.In the chapter 5, the photoionization and dissociative photoionization of ethyl ester at the photon energy range of 15.7-10 eV is presented. The IE of the molecule, CH2=CHCOOCH2CH3, and the AEs of the fragment ions, C5H7O2+, CH2=CHCOOCH2+, CH3CH2OC=O+, CH2=CHCO+, CH3CH2O+, CH3CH2+ and CH2=CH+ are measured from the onsets in the photoionization efficiency spectra. The calculated IE of this molecule is 9.62 eV, using ab initio Gaussian-3 (DFT) procedure. And the experimental IE of ethyl ester is (9.95±0.05 eV).Combined the experimental results with the ab initio calculation, the dissociation channels of the fragment ions C5H7O2+, CH2=CHCOOCH2+, CH3CH2OC=O+, CH2=CHCO+, CH3CH2O+, CH3CH2+ and CH2=CH+ are analyzed. The corresponding dissociation energies are also obtained.In the chapter 6, the photoionization and dissociative photoionization of 2-methyl,methyl acrylate(MMA) at the photon energy range of 15.7-9 eV is presented. The IE of the molecule, CH2=C(CH3)COOCH3, and the AEs of the fragment ions, C5H7O2+, CH2=C(CH3)COO+, CH2=C(CH3)CO+, CH3OC=O+, CH2=C(CH3)+ and CH3+ are measured from the onsets in the photoionization efficiency spectra. The calculated IE of this molecule is 9.31 eV, using ab initio Gaussian-3 (DFT) procedure. And the experimental IE of MMA is 9.70±0.05 eV.Combined the experimental results with the ab initio calculation, the dissociation channels of the fragment ions C5H7O2+, CH2=C(CH3)COO+, CH2=C(CH3)CO+, CH3OC=O+, CH2=C(CH3)+ and CH3+ are analyzed. The corresponding dissociation energies are also obtained.