摘要

我們利用飛秒時間解析能力的螢光混頻系統來進行四並苯及三聯苯激發態能量釋解的研究。以266 nm光源激發，在四並苯的螢光訊號最初有一個迅速的上升成分τ1小於100 fs指派為S3→S1的內轉換；接著出現衰減或上升訊號τ2 = 8.6∼15.7 ps與熱擴散係數呈反向線性關係，因此指派τ2為振動能量鬆弛；最後存在單一衰減曲線τ3約為5 ns，指派為S1激發態的生命期。在三聯苯的螢光訊號中，最初出現一個迅速的上升成分τ1∼0.1 ps，指派為分子內振動能量再分配；接著出現另一個上升訊號τ2 = 6.2∼13.2，與溶劑黏度呈線性關係，證實此步驟為構形緩解過程；最後存在單一衰減訊號τ3 = 0.52∼1.22ns指派為S1激發態的生命期。

利用四並苯與對位三聯苯來比較結構不同時，能量緩解過程的差異。四並苯為一個剛性分子，不管在基態或是激發態皆以D2h存在，並不會有苯基扭曲變形的現象；反觀對位三聯苯，在基態為交錯構形為C2h與D2存在，在激發態共軛效應造成環間C-C鍵增長，克服鄰位氫原子的排斥，以平面構形D2h存在，存在構形變化，並且存在苯基擺動運動。為了研究此兩化合物的激發態能量衰變過程，我們藉由改變溶劑性質，針對黏度、熱擴散係數、介電常數、氫鍵影響，來指認τ2的動力學行為。

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.

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