NH2 inversion potential in the S-0 and S-1 electronic states of aniline: fit to the (ro-)vibrational data and comparison with ab initio and density functional results

An effective one-dimensional Hamiltonian has been determined for the NH2 in version motion in aniline. The anharmonic potential is represented by a qua rtic polynomial, fitted to the experimental vibrational transitions in the electronic states S-0 and S-1. In the S-0 state the barrier height is about 580 cm(-1) and the equilibrium angle between the NH2 and the ring planes i s 44 degrees, while in the S-1 state the potential well is extremely flat w ithout a well-defined equilibrium angle. These results are compared with th ose obtained by ab initio methods. The long-standing discrepancy between th e rotational and vibrational results is partially clarified. (C) 2000 Elsev ier Science B.V. All rights reserved.