Abstract

The role of vibrational coherence in highly efficient, ultrafast electron transfer (ET) systems has recently come under investigation [1]. In the conventional theories for ET the vibrational coordinate plays an essential role: in the Sumi-Marcus theory [2] this mode facilitates ET from the excited state whereas in the Jortner-Bixon theory [3] it provides for additional decay channels in the inverted regime. In these theories it is a priori assumed that these vibrational motions are thermally equilibrated and motion along the reaction coordinate is limited by the longitudinal relaxation time of the solvent. However, recently ultrafast ET has been observed in which the transfer rate greatly exceeds the relaxation time of the solvent. For example in intermolecular ET between nile blue and the electron donating solvent N,N’-dimethylaniline (DMA) the transfer rate is 50 times larger than the solvent dipolar reorientation time [4]. In betaines g the observed ET rates exceed the theoretical predictions by a factor of 10⁸ [5] and subpicosecond ET was recently observed for C₆₀ in DMA [6].

© 1992 The Author(s)