Ultrafast dynamics of the azobenzene-coumarin complex: investigation of cooling dynamics measured by an integrated molecular thermometer.
Ultrafast dynamics of the azobenzene-coumarin complex: investigation of cooling dynamics measured by an integrated molecular thermometer.
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偶氮苯-香豆素复合物的超快动力学：通过集成分子温度计测量的冷却动力学研究。
DOI：
10.1021/jp052501i
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Rodgers,MichaelAJ
中科院分区：
文献类型：
--
作者：
Velate,Suresh;Danilov,EvgenyO;Rodgers,MichaelAJ
以7-氨基-4-三氟甲基香豆素（ATC）为探针，利用飞秒时间分辨紫外吸收光谱研究了光激发偶氮苯（Az）的能量耗散机制。探针分子和Az之间的距离通过刚性脯氨酸间隔物将它们共价连接在一起来固定。用波长为480 nm的100 fs激光脉冲激发四氢呋喃溶液进入S1态，研究了溶液中的皮秒动力学。得到的Az-Pro-ATC的瞬态吸收光谱结合了ATC的S1态吸收和振动激发基态吸收。对Az-Pro-ATC的瞬态光谱进行了S1吸收的修正，得到了ATC热带的时间分辨吸收光谱。在Az-Pro-ATC振动冷却的瞬态动力学中观察到三个主要成分。有人建议，在CA。0.25激发后，偶氮苯的S1态发生衰变，形成Az-Pro-ATC的初始振动激发非热化基态，该基态包含偶氮苯和香豆素的振动模式.这种热基态在ca中衰减。0.32 ps到下一个，振动平衡，通过重新分配分子内的能量瞬态。随后，后一种状态通过将其能量转移到最接近的溶剂分子而冷却。5 ps;然后，能量在13 ps内扩散到本体溶剂。
The energy dissipation mechanism from photoexcited azobenzene (Az) was studied by femtosecond time-resolved UV absorption spectroscopy using 7-amino-4-trifluoromethylcoumarin (ATC) as a probe. The distance between the probe molecule and Az was fixed by covalently linking them together through a rigid proline spacer. Picosecond dynamics in THF solutions were studied upon excitation into the S1state by a 100 fs laser pulse at 480 nm. Transient absorption spectra obtained for Az-Pro-ATC combined the S1state absorption and vibrationally excited ground-state absorption of ATC. Correction of the transient spectrum of Az-Pro-ATC for the S1absorption provided the time-resolved absorption spectrum of the ATC hot band. Three major components were observed in the transient kinetics of Az-Pro-ATC vibrational cooling. It is proposed that in ca. 0.25 ps after the excitation, the S1state of azobenzene decays to form an initial vibrationally excited nonthermalized ground state of Az-Pro-ATC that involves vibrational modes of both azobenzene and coumarin. This hot ground state decays in ca. 0.32 ps to the next, vibrationally equilibrated, transient state by redistributing the energy within the molecule. Subsequently, the latter state cools by transferring its energy to the closest solvent molecules in ca. 5 ps; then, the energy diffuses to the bulk solvent in 13 ps.