Ultrafast formation of an intramolecular cation–pi bond

Ultrafast conformeric dynamics in N,N-dimethylphenethylamine is initiated by photo-excitation to the 3p Rydberg level. On the ion-like potential energy surface of the Rydberg state, the formation of an intramolecular cation–pi bond between the positively charged amine ion core and the aromatic ring is observed in real time using Rydberg fingerprint spectroscopy. The structural dynamics of the cation–pi bond formation proceeds with a 5.3 ps time constant at an internal temperature of 760 K.