Study Of Dissociative Photoionizaiton And Formation Of Secondary Organic Aerosol Of2-methyl-2-butenal

This thesis presents the experimental and theoretical studies of dissociative photoionization of2-methyl-2-butenal, using photoionizatin time-of-Flight mass spectrometer (PI-TOF-MS), and the synchrotron radiation vacuum ultraviolet (SR-VUV) serves as ionization source. Photoionization mass spectrometry is obtained. The ionization energy (IE) of the parent molecule and appearance energies (AE) for the fragment ions are determined by the photoionization efficiency curves (PIEs). With the aid of quantum chemical calculations program, GaussianO9, the dissociation channels to generate the fragment ions are discussed. At last, the formation of secondary organic aerosol (SOA) of2-methyl-2-butenal are studied experimentally.The thesis consists of five chapters:In chapter1, the background of the studies of the2-methyl-2-butenal and SOA is presented, also some of the important concepts in the molecule ionization studies are introduced briefly.In chapter2, the principle and development of sychrontron radiation are summarized. Especially, the capabilities of the National Sychrontron Radiation Laboratory and the Atom and Molecule Physics beam line are described.In chapter3, quantum chemistry theory is described briefly. CBS-QB3method is introduced in detail, which is applied in this thesis.In chapter4, the experimental and theoretical studies of2-methyl-2-butenal are presented. Firstly, the photoionization mass spectrometry of the parent molecule is obtained, then, by scanning the PIEs, the IE of the parent molecule and the AEs of the fragment ions are obtained for the first time ever. With the aid of theoretical calculation, six dissociation channels to form the fragment ions are discussed. H shifting and ring forming are found in the channels, and the methyl group on the a carbon atom is involved in some of the channels. In chapter5, investigation of the research of the detection of SOA are presented in the first part. Then the experimental study on the behavior of2-methyl-2-butenal is carried out in compare with2-propenal. Effect of different factors is then discussed. Also, two theories on the mechanism of the aging process of the aerosol particles are described and compared. On the base of our experiment result, a correcting theory is proposed.