Methanol, Ethanol And Acetone Mixed Clusters Of Laser Ionization Mass Spectrometry

In the past decades, the investigation of cluster science has been developed flying. It possesses signify meanings for understanding the solvent state chemical reaction and looking for the new type of material.The study of molecular cluster is an important direction of cluster science. It may offer crucial information on solvation and liquid chemical reaction. The clusters which are formed through hydrogen-bonded are especially important, due to the hydrogen-bonded not only occur in some solvent, but also biological system. It affects the physical and chemic property of matter greatly. In this paper, we mainly present the following contents.(1) The photoionization process of the methanol-acetone clusters at 355nm was studied using laser multiphoton ionization and a time-of-flight mass spectrometer. A series of protonated clusters (CH₃OH)_nH⁺ , (CH₃COCH₃)_nH⁺, (CH₃OH)_n(CH₃COCH₃)H⁺ and (CH₃OH)_n (CH₃COCH₃)₂H⁺ were measured. We analyzed the character of signal intensity and identified the products were produced from the proton transfer reactions in the binary clusters. Furthermore, possible geometric structures of (CH₃OH)_n(CH₃COCH₃)H⁺ with relatively small sizes were obtained using ab initio calculation method.(2) In the same experiment condition the multiphoton ionization mass spectrum of ethanol-acetone clusters were detected. A series of clusters (C₂H₅OH)_nH⁺, (CH₃COCH₃)_nH⁺, (C₂H₅OH)_n(CH₃COCH₃)H⁺, and (C₂H₅OH)_n(CH₃COCH₃)₂H⁺ were detected. The equilibrium conformations of neutral and ionic clusters were obtained using ab initio calculation. The dissociation channels and dissociation energies of both neutral and ionic CH₃COCH₃-C₂H₅OH clusters were also obtained.(3) Laser ablation-molecular beam (LA-MB) was used to produce the negative cluster ions, (CH₃OH)_nCH₃O^-(n=3-23). Experimental results revealed that these negative cluster ions were mainly formed when the ablating laser acted on the back part of the pulsed molecular beam in temporal dimension, Using ab initio calculations at the B3LYP/6-31G(d) level, we obtained the possible geometric structures of (CH₃OH)_nCH₃O^-(n=0-4), and concluded that the (CH₃OH)₃CH₃O^-is a magic structure.