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 (similar to 42 cm(-1)) and the primary bond-twisting dynamics (similar to 650 fs) for the D-2 state are on a vastly different time scale from that reported (similar to 10 ns) in solution.