The infrared spectrum of the benzene-Ar cation

The infrared (IR) absorption spectra of the jet-cooled C6H6 and C6D6 cations, complexed with Ar, are measured throughout the 450-1500 cm(-1) region via IR-laser-induced vibrational dissociation spectroscopy. The IR spectrum of the C6H6-Ar cation is dominated by a Fermi resonance between the IR active nu(11) mode and two components of the combination mode of the lowest frequency modes nu(6) and nu(16). A stringent upper limit of 316 cm(-1) is found for the value of the dissociation limit D-0 of the neutral C6D6-Ar complex. (C) 1999 American Institute of Physics. [S0021- 9606(99)01548-2].