Inversion tunneling in aniline from high resolution infrared spectroscopy and an adiabatic reaction path Hamiltonian approach

We investigate the influence of all vibrational modes on the NH, inversion tunneling dynamics of aniline. The infrared absorption spectrum of aniline was recorded between 10 and 10000 cm(-1). The spectrum is analysed in terms of a reaction path Hamiltonian using an ab initio potential energy surface . The large amplitude motion is chosen as reaction path and is treated expl icitly on a grid. All other internal degrees of freedom are treated adiabat ically in the harmonic approximation. The theoretical treatment includes as essential extension of previous reaction path treatments the method of dia batic rotations, which decouples degenerate modes occurring at certain valu es of the reaction coordinate.