A supersonic expansion of the title molecule (TDMAE) with helium and polar solvent molecules S (ammonia or acetonitrile) generates TDAME(S)(greater than or equal to10) clusters. By applying the feintosecond pump-probe technique, a wavepacket is launched on the S-1 potential energy surface of TDMAE. The electronic configuration of TDMAE changes from valence V(pipi*) to Zwitterionic C+C- when the wavepacket passes in the vicinity of a conical intersection. While argon as solvent slows down this switch by an inertial effect, the present polar molecules move the conical intersection, reduce the length of the way to access it and accelerate the corresponding V-to-Z energy transfer. (C) 2004 Elsevier B.V. All rights reserved.