Internal rotation in high-resolution ultraviolet spectra. II. Spectrum and structure of the aniline–nitrogen van der Waals complex

Abstract

Rotationally resolved S1←S0 electronic spectra of the nitrogen complex of aniline have been observed. The spectra are split into two subbands due to internal rotation of N2. The analysis of the rotational constants reveals that N2 is located above the ring plane of aniline and in the symmetry plane of aniline in the equilibrium position. Barriers hindering internal rotation have been obtained from fitting experimental transitions frequencies using a semirigid C2v top–Cs frame internal rotation model. Upon excitation into S1, the distance of N2 to the ring decreases and the internal rotation barrier increases by a factor larger than 2. Possible reasons for this behavior are discussed.