1.Shanghai Advanced Research Institute,Chinese Academy of Sciences;2.University of Chinese Academy of Sciences;3.School of Physical Science and Technology,ShanghaiTech University
Science and Technology Commission of Shanghai Municipality (20DZ2210300)
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 375 nm, 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 is 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 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.