Ultrafast relaxation dynamics of excitons in one-dimensional metal complexes

Temperature dependence of the relaxation processes from the photo-excited state in Platinum dimethylglyoxime complex (Pt(dmg)₂) film was investigated by femtosecond pump- probe spectroscopy. Measurements were made at 300K and 80K. The exciton lifetime estimated from the decay of the excited state absorption was 21ps at both temperatures. This suggests that the thermal barrier associated with the relaxation to the ground state is very small. The intensity of bleaching of exciton absorption caused by third order nonlinear susceptibility was about ten times larger at 80K than at 300K. It suggests that an excited state with higher electronic coherence exists at lower temperatures. An ultrafast bleaching component decaying within 400fs which is observed only at 80K is considered to arise from the the electronic coherence of the excited state.