標題: Photoisomerization dynamics of azobenzene in solution with S-1 excitation: A femtosecond fluorescence anisotropy study
作者: Chang, CW
Lu, YC
Wang, TT
Diau, EWG
應用化學系
應用化學系分子科學碩博班
Department of Applied Chemistry
Institute of Molecular science
公開日期: 18-Aug-2004
摘要: Measurements of anisotropy of femtosecond fluorescence after direct excitation of the S-1(npi(*)) state of azobenzene in hexane and ethylene glycol solutions have been carried out to address the controversy about inversion and rotation in the mechanism of photoisomerization. The observed anisotropies in hexane decay to a nonzero asymptotic level with a relaxation period the same as that for slow decay of the corresponding biexponential transient; this effect is attributed to involvement of the out-of-plane CNNC-torsional motion on approach to a twisted conical intersection along the "rotation channel" that depolarizes the original in-plane transition moment. In contrast, when the rotational channel becomes substantially hindered in ethylene glycol, the anisotropies show no discernible decay feature, but the corresponding transients show prominent decays attributed to involvement of in-plane symmetric motions; the latter approach a planar-sloped conical intersection along a "concerted inversion channel" for efficient internal conversion through vibronic coupling. The proposed mechanism is consistent with theoretical calculations and rationalizes both results on quantum yields and ultrafast observations.
URI: http://dx.doi.org/10.1021/ja049215p
http://hdl.handle.net/11536/26466
ISSN: 0002-7863
DOI: 10.1021/ja049215p
期刊: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume: 126
Issue: 32
起始頁: 10109
結束頁: 10118
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