In this Letter, we report the ultrafast dynamics of isomerization and ring opening of azines, using femtosecond-resolved mass spectrometry. The experimental results and theoretical DFT/ab initio calculations elucidate the reaction mechanism and indicate the crucial role of conical intersections in driving these forbidden, ground-state processes. The global motion, initiated by fs wavepackets, is an important concept for nonradiative and reactive processes in polyatomics. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 33]
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