Direct Observation of the Primary Bond-Twisting Dynamics of Stilbene Anion Radical

The anion radicals of stilbenes in the collisionless isolated phase were synthesized by electron attachment, and their dynamics were observed in real time on the femtosecond time scale. The observed coherent vibrational motion (∼42 cm^(−1)) and the primary bond-twisting dynamics (∼650 fs) for the D_2 state are on a vastly different time scale from that reported (∼10 ns) in solution.