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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Spectroscopy of Jet-Cooled Water Complexes with Coumarin 151: Observation of Vibronically Induced Conformational Barrier Crossing
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Spectroscopy of Jet-Cooled Water Complexes with Coumarin 151: Observation of Vibronically Induced Conformational Barrier Crossing

机译：香豆素151的喷射冷却的水配合物的光谱学：观察到的玻璃纤维诱导的构象性障碍穿越

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摘要

Coumarin 151, when complexed 1:1 by a water molecule in a supersonic jet, develops two sets of resonances, based on features displaced by -45 cm↑(-1) (species A) and -690 cm↑(-1) (species B) from the uncomplexed molecule. The vertical ionization thresholds of these species differ by a much greater amount (0.5 the bound states, confirming that the attachment sites are functionally different. When two water molecules are present, there appears to be a single cluster type, having an origin shifted from the bare chromophore by - 1214 cm↑(-1); In this case, fluorescence excitation spectra recorded simultaneously at two emission wavelengths show that the 2:1 species exhibit a Stokes shift for excitation energies≥60 cm↑(-1) . Also, above this energy barrier, the ionization energy shifts downward by＞1000 cm↑(-1) The bare molecule also undergoes vibronically induced nonradiative relaxation, but this occurs at higher energies (i.e., >450 cm↑(-1) ) and results in a large increase in the effective ionization threshold. The fluorescence decay time of the 2:1 water aggregate,excited into the zero-point level of S↓(1), was found to be twice that of the bare molecule (6.7 ns vs 3.5 ns). Above the relaxation barrier, the decay time of the initial state rapidly decreased below the instrument resolution of 35 ps. On the other hand, the fluorescence decay time of the product state increased to ≈9.5 ns and remained constant up to >400 cm↑(-1) excess vibrational energy.
机译：香豆素151在超音速射流中与水分子1：1配合时，会基于-45 cm↑（-1）（物种A）和-690 cm↑（-1）（物种B）来自复杂的分子。这些物质的垂直电离阈值相差很大（0.5的键合态，证实了附着位点在功能上是不同的。当存在两个水分子时，似乎只有一个簇类型，其原点从裸发色团--1214 cm↑（-1）;在这种情况下，在两个发射波长处同时记录的荧光激发光谱显示，激发能量≥60cm↑（-1）的2：1物种表现出斯托克斯位移。在此能垒之上，电离能向下移动> 1000 cm↑（-1）裸分子也经历了玻璃纤维诱导的非辐射弛豫，但这发生在更高的能量（即> 450 cm↑（-1））上，并导致有效电离阈值大幅增加，激发到S↓（1）的零点水平的2：1水团聚体的荧光衰减时间是裸分子的两倍（6.7 ns vs 3.5 ns）。在弛豫壁垒之上，th初始状态的衰减时间迅速降低到35 ps的仪器分辨率以下。另一方面，产物态的荧光衰减时间增加到≈9.5ns，并且在> 400 cm↑（-1）的多余振动能时保持恒定。

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