| In the research field of cluster, hydrogen bond clusters science is a rather active research field. Hydrogen bonds exist in the most important solvent-water and many biomolecules interact with water by hydrogen bonds. There are lots of biomolecules take on their functions and structures by hydrogen bonds. Thus, the study of hydrogen bonds in water, hydrogen bonds formed between biomolecules and water, and hydrogen bonds in biomolecules, is of special importance.For the investigations of hydrogen-bonded clusters, many scientists have done much meaningful work. This dissertation presents the detailed results about the investigations of photoionization mechanisms of a series of hydrogen-bonded clusters, which were performed using nano- or femtosecond laser and time-of-flight mass spectrometer as well as ab initio calculations. The following points are mainly concerned:1. To observe intracluster chemical reaction phenomena after ionization, including charge transfer, proton transfer, Penning ionization, vibrational predissociation; to discuss the photoionization mechanisms; to understand the effects of the cluster formation on the monomer; to investigate the microscopic mechanism of some important processes such as charge transfer, proton transfer, and hydrogen atom transfer. Due to the proton transfer reaction is very meaningful in life science, some molecules to be studied are specially selected among molecules relating with some units in biomolecules.2. The proton transfer reactions in weak hydrogen-bonded clusters are paid more attention to. At the same time, some femtosecond laser photoionization experimental results were compared with some relevant nanosecond experimental results.3. To study what effects the formation of clusters has on physical, chemical properties of a molecule, such as structure, ionizaion potential, proton affinity, dissociation energy; to understand the change of molecular properties with increasing cluster size, including dissociation channel, dissociation energy, intracluster vibrational frequency, ionization potential and proton affinity, etc.The principal results obtained are listed as follows:(1) The multiphoton ionization mechanisms of hydrogen-bonded cluster systems: pyrimidine-(methanol)n and pyridazine-(methanol)n were studied using TOP mass spectrometer at 355 and 532 nm laser. Only a sequence of protonated cluster ions C4H4N2-(CH3OH)nH was measured. The relevant unprotonated C4H4N2-(CH3OH)n+, however, was not measured. The neutral and ionic stable structures of the two kinds of clusters were obtained by use of HF and DFT methods. The theoretical results indicates that when the two kinds of hydrogen-bonded clusters are vertical ionized, an intracluster proton transfer reaction can occur quickly, then dissociated to produce dominantly the protonated clusterions. Not only the hydrogen atom of hydroxyl but also the hydrogen atom of the methyl group can transfer to the N atom of heterocycle. But in the latter case, an intracluster rearrangement is needed. Thus, there is a high energy barrier to be overcomed during the transfer process, which makes the reaction unfavorable. Within the proton cluster ion C4H4N2-(CH3OH)H+, the proton prefers to link with the N atom.(2) The multiphoton ionization experiments of pyrimidine-(water),, cluster were performed firstly under supersonic jet. Due to the low saturation atmosphere of pyrimidine at normal temperature, some analogous experiments of others were failed. By taken some measures to provide a higher and more stable temperature, we have done the experiments successfully.The multiphoton ionization mass spectra of pyrimidine-(water)n at 355 and 532 nm laser show a sequence of C4NO and no relevant unprotonated cluster ions C4H4N2-(H2O)n+ . After changing some experimental conditions, such as laser power, it is still the result. Both the experimental and theoretical results show that the production of protonated cluster ions related more to the excitation or ionization of water unit, namely, an intracluster Pennin...
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