Intracluster ion-molecule reaction

Based on the AID mechanism, the neutral clusters are ionized through multiphoton ionization and the protonated clusters are formed through the intracluster ion-molecule reaction between NH3 and the neighboring NH3 species as expressed in the following ... 

The observed H+(NH3)n and H (NH3)n(PA) clusters are thought to be formed in a two-step reaction sequence taking place after ionization of the PA(NH3) cluster. The first step is a charge transfer (CT) reaction between the resonantly ionized PA+ and the NH3 molecules in the cluster. The second step is an intracluster ion-molecule reaction (ICIMR) of the charged ammonia cluster leading to the formation of an (n - 1) protonated cluster ion this has been previously established for NH3 clusters33 and is sufficiently exothermic for fragmentation of the cluster. 

Pulse electron-beam mass spectrometry was applied by Kebarle, Hiraoka, and co-workers766,772 to study the existence and structure of CH5+(CH4) cluster ions in the gas phase. These CH5+(CH4) clusters were previously observed by mass spectrometry by Field and Beggs.773 The enthalpy and free energy changes measured are compatible with the Cs symmetrical structure. Electron ionization mass spectrometry has been recently used by Jung and co-workers774 to explore ion-molecule reactions within ionized methane clusters. The most abundant CH5+(CH4) cluster is supposed to be the product of the intracluster ion-molecule reaction depicted in Eq. (3.120) involving the methane dimer ion 424. 

Intracluster ion-molecule reactions have been the subject of numerous investigations (see other chapters of this book). However, in this chapter, we will focus only on aromatic nucleophilic substitutions in substituted benzene/molecule clusters where the two-photon ionization process allows us to obtain spectroscopic information on the parent cluster involved in the reaction process. 

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