Abstract
Abstract We use the femtosecond fluorescence frequency up-conversion system to investigate tetracene and p-terphenyl excited state energy relaxation process. The photo source stimulates by 266 nm, to detect tetracene fluorescence signal. At first some rapid rise lifetime τ1 is smaller than 100 fs assigns to internal conversion from S3 to the S1 state. Then presents the decay or the rise signal τ2 = 8.6~15.7 ps and the thermal diffusivity assumes the reverse linear relationship, therefore τ2 assigns to vibration cooling. Finally the existence single exponential decay curve τ3 approximately is 5 ns, the designation is the S1 excited state lifetime. In p-terphenyl fluorescence signals. At first presents a rapid rise lifetime τ1 = 0.6~0.19 ps, assigns to intramolecular vibrational redistribution. Then presents another rise signal τ2 = 6.2~13.2 ps, presents a dependence on solvent viscosity, confirms this step for the geometric relaxation process. Finally the existence single exponential decay curve τ3 = the 0.62~1.22 ns designation is the S1 excited state emission lifetime. Compare using tetracene and p-terphenyl when the structure is different, energy relaxation process difference. tetracene is a rigid member, no matter in the ground state perhaps the excited state all by D2h symmetry existence, will not have the phenomenon which the distortion will distort. Reviews p-terphenyl, to interlock the configuration in the ground state is C2h and the D2 existence, in the excited state π conjugated effect causes between the link the C-C band to grow, overcomes the ortho-position hydrogen atom the repel, by the plane configuration D2h existence, existence configuration change. In order to study this two compound the excited state energy relaxation process, we use the change solvent nature, in view of the viscosity, the thermal diffusivity, dielectric constant, the protic solvent influence, assign to τ2 dynamics behavior.