Alcohol - Ether Clusters Multiphoton Ionization Mass Spectrometry Studies

Cluster is a transition state between the single molecule (atom) and condensation state, it represents the initial phase of condensation product. The hydrogen bond is one of the basic chemical forces, and effects the solvation, energy transfer, chemical reaction and so on. So the hydrogen bond cluster's structure analysis, intra-cluster proton transfer reaction guide us to understand the complex life phenomenon and mechanics from a simple level.In this article, we combine the pulsed molecule beam, time of flight mass spectrum and the procedure of Gaussian 03 to research the multiphoton ionization of methanol (ethanol) and diethyl ether cluster.(1) Diethyl ether clusters were studied using both laser multiphoton ionization mass spectrum and supersonic pulsed molecular beam technique. Only less intensity ions of (E)H⁺, (E)₂⁺ and (E)₂H⁺ (E means CH₃CH₂OCH₂CH₃), accompanying with some stronger fragment ions of diethyl ether, were observed. According to the energy calculation, we find that the diethyl ether clusters are formed by weak dipole-dipole interaction and the initially formed dimmer acts as a seed for further cluster growth, the protonated cluster of diethyl ether has a magic number '2'. Meanwhile, the binding energy decreases with size increasing, so larger clusters are not easy to be observed in experiment.(2) In the multiphoton ionization experiment of methanol—diethyl ether, a series of protonated products, (CH₃OH)_n-1(E)H⁺(n=1-7), (CH₃OH)_n-1(E)₂H⁺ (n=1-6) and (CH₃OH)_nH⁺(n=1-8), were observed. According to the optimized structures of (CH₃OH)_n-1(E)⁺ (n=2-4), we considered that the clusters completed the proton transfer through lossing CH₃O, and the ionization happened on the methanol molecular, this result is unexpected. (CH₃OH)_n-1i(E)H⁺(n=2-4) clusters' optimized structure is chain, and doesn't exist the magic number. Otherwise, using the energy calculation, we obtained that the mixed clusters have the similar proton transfer process to alcohol, and discussed the cluster's stability, too. (3) In the multiphoton ionization mass spectrum of ethanol-diethyl ether, only (E)_nH⁺(n=1-3) and (C₂H₅OH)(E)_1,2H⁺ were observed. The optimized structures of (C₂H₅OH)_n-1(E)⁺ and (C₂H₅OH)_n-1(E)H⁺(n=2-4), ionized clusters' ionization position, the proton transfer process and cluster's stability are similar to methanol- diethyl ether cluster.