Knowledge Bank

Two peaks in the p-methylanilne fluorescence excitation spectrum show an unusual splitting that is not evident in the other vibrational bands, or in the aniline spectrum. These bands both display a large deuterum shift $(-200cm-1)$ in the $ND2$ molecule and are thus attributed to the inversion and torsion of the amine group. The presence of the splittings in the amine modes in p-methylanllne, coupled with its absence in the bare aniline suggests that the methyl torsion may be coupled to the mine motion at the opposite end of the ring. Supporting evidence for this interpretation will be presented.