STRUCTURE AND VIBRATIONAL DYNAMICS OF ANILINE AND ANILINE-AR FROM HIGH-RESOLUTION ELECTRONIC SPECTROSCOPY IN THE GAS-PHASE

Rotationally resolved S-1<--S-0 electronic spectra of aniline and its single atom van der Waals complex with argon (An-Ar) have been observe d. Analysis of these spectra leads to a determination of the vibration ally averaged structures of the bare molecule and the complex in the t wo electronic states. Aniline itself is pyramidally distorted at the N H2 group in the S-0 state. Attachment of the Ar atom on the side of th e ring opposite the two N-H bonds converts the symmetric double well a long the inversion coordinate into an asymmetric one, in the ground st ate. The excited state is quasiplanar along this coordinate. Analyses of the spectra of An-Ar at higher energies in the S-1 state provide a probe of the vibrational predissociation (VP) behavior of the complex. We observe in these spectra line broadenings and spectral perturbatio ns from which the important role of inaa-intermolecular mode mixing (i .e., IVR) in promoting the VP process is elucidated. (C) 1996 American Institute of Physics.