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Ultrafast investigation of excited-state dynamics in trans-4-methoxyazobenzene studied by femtosecond transient absorption spectroscopy
zhangsong
Author NameAffiliationE-mail
zhangsong State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China zhangsong@wipm.ac.cn 
Abstract:
The ultrafast photoisomerization and excited-state dynamics of trans-4-methoxyazobenzene (trans-4-MAB) in solutions were investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations. After excited to the S2 state, the two-dimensional transient absorptions spectra show that cis-4-MAB is produced and witnessed by the permanent positive absorption in 400-480 nm. Three decay components were determined to be 0.11, 1.4 and 2.9 ps in ethanol, and 0.16, 1.5 and 7.5 ps in ethylene glycol, respectively. The fast component is assigned to the internal conversion from the S2 to S1 state. The others relaxation pathways are correlated with the decay of the S1 state via internal conversion and isomerization, and the vibrational cooling of the hot S0 state of the cis-isomer. Comparing of the dynamics in different solvents, we demonstrated that the photoisomerization pathway undergoes as the inversion mechanism rather than the rotation mechanism.
Key words:  Photoisomerization, trans-4-methoxyazobenzene, Femtosecond transient absorption spectroscopy
FundProject:
Ultrafast investigation of excited-state dynamics in trans-4-methoxyazobenzene studied by femtosecond transient absorption spectroscopy
zhangsong
摘要:
The ultrafast photoisomerization and excited-state dynamics of trans-4-methoxyazobenzene (trans-4-MAB) in solutions were investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations. After excited to the S2 state, the two-dimensional transient absorptions spectra show that cis-4-MAB is produced and witnessed by the permanent positive absorption in 400-480 nm. Three decay components were determined to be 0.11, 1.4 and 2.9 ps in ethanol, and 0.16, 1.5 and 7.5 ps in ethylene glycol, respectively. The fast component is assigned to the internal conversion from the S2 to S1 state. The others relaxation pathways are correlated with the decay of the S1 state via internal conversion and isomerization, and the vibrational cooling of the hot S0 state of the cis-isomer. Comparing of the dynamics in different solvents, we demonstrated that the photoisomerization pathway undergoes as the inversion mechanism rather than the rotation mechanism.
关键词:  Photoisomerization, trans-4-methoxyazobenzene, Femtosecond transient absorption spectroscopy
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