Comparative study of the binary clusters of acetic acid–water and acetic acid–benzene using electron impact and multiphoton ionization techniques

Abstract

Electron impact and multiphoton ionization techniques are used for a comparative study of the acetic acid–water and acetic acid–benzene clusters generated by supersonic beam expansion. In acetic acid–water clusters, hydrogen-bonding interaction is the driving force in determining the structures of the clusters. The protonated and the methyl cation containing clusters are characterized by 6-membered cyclic and 8-membered bicyclic structures. The similar magic number patterns observed for the protonated and methyl cation containing clusters suggest that the cyclic structures are stabilized by the charge interaction. A remarkable periodicity in the ion intensity of benzene (acetic acid) n clusters is observed. The clusters containing an even number of acetic acid molecules exhibit enhanced ion intensities. This effect is attributed to the formation of multiple cyclic dimers as a result of clustering from a dimer-rich vapor phase. Protonated acetic acid clusters are generated following the three-photon absorption by the binary clusters, which leads to dissociative charge transfer followed by proton transfer within the ionized acetic acid clusters. Evidence is presented for the special stability of the B 2A 8 ion, which is proposed to consist of a benzene dimer cation entrapped between two acetic acid tetramers.