A combined application of femtosecond broadband time-resolved fluorescence (fs-TRF), fluorescence anisotropy (fs-TRFA) and fs to microsecond (mu s) transient absorption (TA) have been used to probe directly the dynamics, nature, formation and decay paths of the singlet intramolecular charge transfer ((ICT)-I-1) state of methyl 4-dimethylaminobenzoate (1a) in acetonitrile. The result reveals explicit evidence for a common electronic origin (the L-a nature) of the (ICT)-I-1 state and its precursor the locally excited ((LE)-L-1) state to account jointly for the dual florescence known to this system. It also shows that the ICT reaction from the (LE)-L-1 to (ICT)-I-1 state occurs with time constant of similar to 0.8 ps and the (ICT)-I-1 state formed decays with a similar to 1.9 ns time constant leading mainly to a pi pi* natured triplet state (T-3(1)). The T-3(1) then relaxes with a similar to 4 mu s lifetime under deoxygenated condition resulting in full recovery of the ground state (S-0). As a case study, this work contributes novel experimental data for improved understanding of the mechanism of ICT reaction; it also reveals a distinct deactivation pattern for this prototype para-amino substituted aromatic carbonyl compound in acetonitrile. ; Department of Applied Biology and Chemical Technology