Non-radiative relaxation of UV photoexcited phenylalanine residues: probing the role of conical intersections by chemical substitution

A conformation-selective photophysics study in phenylalanine model peptides, combining pump-probe gas phase experiments and excited state calculations, highlights for the first time the quenching properties of a primary amide group (through its n pi* excited state) along with the effect of vibrational energy that facilitates access to the conical intersection area.