Infrared spectroscopy of jet-cooled neutral and ionized aniline-Ar

We report the infrared (IR) absorption spectrum of the jet-cooled neutral aniline-Ar Van der Waals complex together with that of the aniline-Ar cation in the 350-1700 cm(-1) range. The spectra are measured using mass-selective ion detection in two different IR-ultraviolet double-resonance excitation schemes, using a free-electron laser as a source of widely tunable, intense IR radiation. A comparison with calculated IR spectra of the bare neutral aniline and of the cation of aniline allows for an unambiguous assignment of all the observed modes. The dissociation limit of the neutral aniline-Ar complex is bracketed between 273 and 329 cm(-1), significantly lower than previously estimated. (C) 1999 American Institute of Physics. [S0021-9606(99)02504-0].