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.

Y.I. received financial support from JSPS Research Fellowships for Young Scientists.

This is a postprint of an article published by Elsevier B.V. in Chemical Physics Letters, 1997, available online: http://doi.org/10.1016/S0009-2614(97)00964-0