Vibrational Energy Flow between Modes by Dynamic Mode Coupling in THIATS J-Aggregates

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• 作者：Daisuke Hasegawa ; Kazuaki Nakata ; Eiji Tokunaga ; Kotaro Okamura ; Juan Du ; Takayoshi Kobayashi
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：November 14, 2013
• 年：2013
• 卷：117
• 期：45
• 页码：11441-11448
• 全文大小：508K
• 年卷期：v.117,no.45(November 14, 2013)
• ISSN：1520-5215

文摘

We performed ultrafast pump鈥損robe spectroscopy of J-aggregates of 3,3鈥?disulfopropyl-5,5鈥?dichloro-9-ethyl thiacarbocyanine triethylammonium (THIATS), one of the most typical cyanine dyes, and detected excited molecular vibrations, using a sub-10 fs pulse laser. The time-resolved two-dimensional difference absorption (螖A) spectra are observed between 鈭?14 and 1267 fs. By performing the Fourier transform and spectrogram analysis, vibrational modes in THIATS are observed at 285, 485, 555, 824, and 1633 cm^鈥? and there was a modulation of the vibrational frequencies around 1633 cm^鈥? which depend on the delay time, respectively. By the analysis of the modulation, energy flow is found to take place from other modes to the 1633 cm^鈥? mode through the low frequency mode with 50 cm^鈥?. Also, by fitting the real-time traces of 螖A with the sum of two exponential functions and a constant term, the average lifetimes of three electronically excited states were found to be 蟿₁ = 52 卤 5 fs and 蟿₂ = 540 卤 78 fs. By performing single-exponential fitting around the stationary absorption peak at 1.990 eV, in the negative time range, the electronic dephasing time, T₂^ele, is determined to be 18.30 fs.