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利用飞秒瞬态吸收光谱技术研究了反式对氨基偶氮苯(AAB)溶解在乙醇中的超快激发态动力学.当利用400 nm光激发分子到S2态后,由S211102412相似文献   
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孙四梅  张嵩  宋娇  郭小珊  江超  孙静俞  王赛玉 《中国物理 B》2022,31(2):27803-027803
The excited-state intramolecular proton transfer of 2-(2-hydroxyphenyl)benzoxazole dye in different solvents is investigated using ultrafast femtosecond transient absorption spectroscopy combined with quantum chemical calculations.Conformational conversion from the syn-enol configuration to the keto configuration is proposed as the mechanism of excited-state intramolecular proton transfer.The duration of excited-state intramolecular proton transfer is measured to range from 50 fs to 200 fs in different solvents.This time is strongly dependent on the calculated energy gap between the N-S;and T-S;structures in the S;state.Along the proton transfer reaction coordinate,the vibrational relaxation process on the S;state potential surface is observed.The duration of the vibrational relaxation process is determined to be from8.7 ps to 35 ps dependent on the excess vibrational energy.  相似文献   
3.
The twisted intramolecular charge transfer and the excited state relaxation of 1-aminoanthraquinone(1-NH_2-AQ)in different solvents are investigated using quantum chemical calculations in this paper.The geometries of the ground state are optimized both in gas and solvents based on the high-level ab initio calculations,the lowest excited singlet state geometry is optimized only in gas for simplicity.An intramolecular charge transfer property is substantiated by the large change of dipole moments between the S_0 and S_1 states.The mechanism of twisted intramolecular charge transfer is proposed by the conformational relaxation on the potential surface of the S_1state.Quantum chemical calculations present that internal conversion and intersystem crossing are important approaches to the ultrafast deactivation of the S_1 state via the twisting of the amino group.The smaller energy difference between the S_0 and S_1 state shows that the internal conversion process is much faster in a polar solvent than in a nonpolar solvent.Energy intersections between the T_2 and S_1 state in cyclohexane and dioxane indicate a faster intersystem crossing process in them than in ethanol.These theoretical results agree well with the previous experimental results.Energy barriers are predicted on the potential surface of the S_1 state,and they have a positive correlation to solvent viscosity,and the timescale of twisted intra-molecular charge transfer in dioxane is predicted to be longer than in cyclohexane and ethanol.  相似文献   
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利用飞秒瞬态吸收光谱结合量化计算研究了1-羟基蒽醌在溶剂中的激发态分子内质子转移动力学. 分子受到400 nm光激发后的瞬态吸收谱呈现出激发态吸收和受激辐射两个光谱带. 受激辐射信号较激发态吸收信号滞后出现,由此确定质子转移时间是32 fs. 量化计算表明分子在沿质子转移路径衰变时,分子轨道和能级次序发生了反转,形成锥形交叉. 在质子转移之后,经锥形交叉布居的电子态发生内转换和分子间能量弛豫,时间分别是200 fs和16 ps. 基态回复时间是300 ps. 通过实验和理论研究,证实存在两个质子转移路径,其中主要的衰变路径保持了原来轨道的性质.  相似文献   
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