We have investigated reactivity of double bond in 2-methyl-2-butene (also trimethylethylene or amylene) in the excited and ionized states. In a combined experimental and theoretical study, we focused on both the intermolecular and intramolecular reactions. In a molecular beam experiment, we have sequentially picked up several amylene molecules on the surface of argon nanoparticles ArM, M̅ ≈ 90, acting as a cold support. Ionization with 70 eV electrons yields mass spectra strongly dominated by amylene cluster ions Am(Am)n+. Interestingly, upon multiphoton ionization with 193 nm (6.4 eV) photons, a new strong fragment series appears in the spectra, nominally corresponding to an addition of two carbon atoms, i.e., (Am)nC2+. This difference between electron and photoionization suggests a reaction in an excited state of amylene with a neighboring amylene molecule. We used techniques of nonadiabatic molecular dynamics to study the reactivity of amylene molecules both in the excited and in ionized states. Possible reaction pathways are proposed, substantiating the observed differences between the electron ionization and photoionization mass spectra.

中文翻译：

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游离氩纳米粒子簇上亚芳基双键的光化学。

我们研究了在激发态和离子化态的2-甲基-2-丁烯（也为三甲基乙烯或戊烯）中双键的反应性。在结合实验和理论研究的过程中，我们集中于分子间和分子内反应。在分子束实验中，我们顺序地在氩纳米颗粒ArM上提取了几个亚甲基分子，M̅≈90，用作冷载体。用70 eV电子电离产生的质谱图主要由亚芳簇离子Am（Am）n +支配。有趣的是，在用193 nm（6.4 eV）光子进行多光子电离时，光谱中出现了一个新的强片段系列，名义上对应于两个碳原子即（Am）nC2 +的加成。电子和光电离之间的这种差异表明，在亚芳基的激发态下，其与相邻的亚芳基分子发生了反应。我们使用非绝热分子动力学技术来研究戊烯分子在激发态和电离态下的反应性。提出了可能的反应途径，证实了在电子电离质谱和光电离质谱之间观察到的差异。