Doubly charged fragment ions in the field ionization mass spectra of alkylbenzenes

It is shown that the radical [C₆H₅C_mH_2m]²⁺ fragment ions found in the field ionization mass spectra of alkylbenzenes are formed via a different adsorption state of the singly charged species than in the case of the formation of [M]²⁺ molecular ions. It is further demonstrated that the primary fragmentation of molecules by the cleavage of C? C bonds results not only from decompositions of molecular ions in the gas phase but also from surface reactions.