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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Infrared photodissociation spectroscopy of protonated acetylene and its clusters
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Infrared photodissociation spectroscopy of protonated acetylene and its clusters

机译：质子化乙炔及其团簇的红外光解离光谱

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摘要

The protonated acetylene cation, C2H3+, (also known as the vinyl cation) and the proton-bound acetylene dimer cation (C4H5+) are produced by a pulsed supersonic nozzle/pulsed electrical discharge cluster source. The parent ions are also generated with weakly attached argon "tag" atoms, e.g., C2H3+Ar and C4H5+Ar. These ions are mass selected in a specially designed reflectron time-of-flight mass spectrometer and studied with infrared laser photodissociation spectroscopy in the 800-3600 cm(-1) region. Vibrational resonances are detected for both ions in the C-H stretching region. C2H3+ has a strong vibrational resonance near 2200 cm(-1) assigned to the bridged proton stretch of the nonclassical ion, while C4H5+ has no such free-proton vibration. Instead, C4H5+ has resonances near 1300 cm(-1), consistent with a symmetrically shared proton in a di-bridged structure. Although the shared proton structure is not the lowest energy isomer of C4H5+, this species is apparently stabilized under the supersonic beam conditions. Larger clusters containing additional acetylene units are also investigated via the elimination of acetylene. These species have new IR bands indicating that rearrangement reactions have taken place to produce core C4H5+ ions with the methyl cyclopropane cation structure and/or the protonated cyclobutadiene isomer. Ab initio (MP2) calculations provide structures and predicted spectra consistent with all of these experiments.
机译：质子化的乙炔阳离子C2H3 +（也称为乙烯基阳离子）和质子键合的乙炔二聚阳离子（C4H5 +）是由脉冲超音速喷嘴/脉冲放电簇源产生的。母离子也产生有弱连接的氩“标签”原子，例如C 2 H 3 + Ar和C 4 H 5 + Ar。这些离子是在专门设计的反射式飞行时间质谱仪中进行质量选择的，并在800-3600 cm（-1）范围内通过红外激光光解离光谱法进行了研究。在C-H拉伸区域中检测到两种离子的振动共振。 C2H3 +在2200 cm（-1）附近具有很强的振动共振，该共振被分配给非经典离子的桥接质子拉伸，而C4H5 +没有这种自由质子振动。相反，C4H5 +在1300 cm（-1）附近具有共振，这与双桥结构中对称共享的质子一致。尽管共享的质子结构不是C4H5 +的最低能量异构体，但该物种显然在超声束条件下稳定了。还通过消除乙炔，研究了含有其他乙炔单元的较大簇。这些物质具有新的IR谱带，表明发生了重排反应，以产生具有甲基环丙烷阳离子结构和/或质子化的环丁二烯异构体的核心C4H5 +离子。从头算（MP2）计算可提供与所有这些实验一致的结构和预测光谱。

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