Infrared Depletion Spectroscopy of the Aniline Dimer

The infrared depletion spectrum of the aniline dimer, formed in a supersonic jet, has been recorded in the N−H stretch region by combining infrared laser excitation and resonant two-photon ionization/time-of-flight mass spectrometry. Only two bands have been found at 3394.0 and 3465.9 cm -1 (±0.5 cm -1 ) in the region 3130−3530 cm -1 . These are red-shifted by 27.8 and 42.3 cm -1 from the symmetric and asymmetric NH stretching vibrations of the aniline monomer, respectively. A configuration with mutual NH 2 ···π bonds and phenyl groups stacked in parallel is suggested for the ground-state aniline dimer.