Anomalous conformer dependent S1 lifetime of l-phenylalanine

The fluorescence lifetimes were measured for six conformers of l-phenylalanine cooled in a supersonic jet. It was found that the S1 state lifetimes differ by a factor of three among the conformers. Especially, the most stable conformer (intramolecular hydrogen-bonded form) in S0 had the shortest lifetime. Time-dependent DFT calculation suggested an importance of the mixing of the nπ∗ character to S1(ππ∗) in this conformer dependent dynamics.