三种状态蒽的三重态吸收性质研究

Study on the Triplet State Absorption Properties of Three States of Anthracene

摘要:

利用瞬态吸收光谱技术研究了蒽在甲苯溶液和PMMA薄膜及晶体中的瞬态吸收过程,发现当激发波长375nm处的吸收度为0.7时,溶液中蒽的三重态最大吸收信号强度为其在PMMA中的5倍,而在高吸收度的晶体中,三重态吸收较低。通过建立模型分析,PMMA中的蒽分子存在光场诱导下偶极矩的宏观统计极化,导致宏观极化偶极矩的降低,而处于甲苯溶液中的蒽分子则易被光场所极化,产生较大的极化偶极矩,这是引起三重态吸收信号差异的原因。在晶体状态下,S₁能级发生分裂,低于T₂能级,S₁-T₁能量差较大,系间窜越失效,抑制了三重态吸收。以上结果解释了蒽分子在不同状态下三重态最大吸收信号差异。

Abstract:

The transient absorption process of anthracene in toluene solution, PMMA film and crystal was studied by transient absorption spectroscopy. It was found that when the absorption was 0.7 at the excitation wavelength of 375nm, the maximum absorption signal intensity of the triplet state of anthracene in solution was five times that in PMMA. In the crystal with high absorption, the triplet state absorption signal was lower. By establishing a model, it was found that the anthracene molecules in PMMA exhibited macroscopic statistical polarization of the induced dipole moment under the optical field, resulting in a decrease in macroscopic polarization dipole moments. On the other hand, the anthracene molecules in the toluene solution were easily polarized by the optical field, resulting in a larger polarized dipole moment. This is the reason for the difference in triplet state absorption signals. In the crystal state, the S₁ energy level splits and is lower than T₂. The energy gap between S₁ and T₁ is large, and the intersystem crossing is not effective, which inhibits the absorption of the triplet state. These results explain the difference in the maximum absorption signal of the triplet state of anthracene in different states.