Infrared depletion spectroscopy of aniline dimer cation and aniline-benzene cation clusters

The vibrational spectra of the NH stretching modes of the aniline dimer cation and the aniline-benzene cluster cation have been measured by infrared depletion spectroscopy, which utilizes infrared multiphoton decomposition of the cluster ions and resonance-enhanced multiphoton ionization-time-of-flight (REMPI-TOF) mass spectrometry. Two strong absorption bands were observed at 3440 and 3305 cm(-1) in the infrared spectrum of the aniline-benzene cluster cation, while the infrared spectrum of the aniline dimer cation exhibited only one strong peak at 3415 cm(-1) in the region between 3200 and 3600 cm(-1). A hydrogen bonded structure between one of the NH bonds of the aniline cation and the benzene ring for the aniline-benzene cluster ion, and that between the NH bond of the aniline cation and the lone pair of the nitrogen atom of neutral aniline for the dimer cation have been proposed. (C) 1997 Elsevier Science B.V.