Femtosecond to nanosecond relaxation time scales in electronically excitedtetrakis(dimethylamino)ethylene: identification of the intermediates

In the TDMAE molecule (title molecule), the time evolution has been analyze d from the very initial excitation step down to a fluorescent state, over w idely different time scales. Pump probe measurements have been performed at 3 different excitation wavelengths 400, 266 and 200 nm. The decay has been followed over the femtosecond and subnanosecond ranges with this method an d the decay of the final charge transfer state has been detected by its flu orescence emission. This allows an overview of the complete decay mechanism . The initial relaxation pathway is interpreted in a similar way to ethylen ic molecules, where the initial wavepacket is quickly trapped in a doubly e xcited state Z with charge transfer character. Then the Z state decays slow ly (10-100 picoseconds) into the final state. In difference to monoalkenes the final stage of this evolution is a charge transfer state. The decay of transient Z state to the charge transfer state is a further assessment of t he partial ionic character of the Z state. This type of molecule with low i onization potential can be viewed as a demonstrative example of the interre lation between the charge induced forces and the deformations in excited st ate reaction dynamics.