Infrared photodissociation spectroscopy of benzene trimer ions. Switching of the dimer ion core in vibrationally excited states

A vibrational spectrum of benzene trimer ion, (C6H6)3+, was measured in the 2900–3100 cm−1 region by infrared photodissociation spectroscopy. An intense band at 2986 cm−1 was attributed to a CH stretching vibration of the dimer ion core in (C6H6)3+. The spectra of isotopically mixed benzene trimer ions with benzene-d6 molecules were also obtained. From the analysis of asymmetric band shape, a switching of the dimer ion core is proposed to occur in the vibrationally excited state prior to the vibrational predissociation.