ULTRAFAST ELECTRON-TRANSFER OF BETAINE-30

After excitation of betaine-30 with a femtosecond pulse, the electron transfer back to the ground state is calculated in a density matrix fr amework. This allows us to investigate radiationless transitions to th e ground state mediated by electronic coupling between excited and gro und state and by coupling to the solvent environment. A single vibrati onal degree of freedom of betaine-30 is treated explicitly, while othe r internal modes and the solvent environment are modeled as a heat bat h of oscillators coupled bilinearly to the internal vibration of the m olecule. The temperature dependence of the transfer rate indicates an increase of electronic coupling between ground and excited state with increasing temperature. (C) 1998 Elsevier Science B.V. All rights rese rved.