Ionization of methane clusters in helium nanodroplets.
Ionization of methane clusters in helium nanodroplets.
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氦纳米液滴中甲烷簇的电离。
DOI：
10.1002/cphc.201100880
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Leidlmair C
中科院分区：
文献类型：
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作者：
Leidlmair C
首次利用高分辨质谱研究了掺甲烷团簇的氦液滴的电子电离。喷射到气相中的主要离子产物是未质子化的（CH 4）n+团簇离子沿着质子化的离子CH 5+（CH 4）n−1。质谱显示了幻数的明确证据，这与二十面体壳层闭合大致一致。然而，观察到了不寻常的特征，包括CH 5+（CH 4）n−1（n=55，148）与（CH 4）n+（n=54，147）相比的不同幻数。对其中一些差异提出了可能的解释。还观察到离子-分子化学的[C2 Hx（CH 4）n]+型产物，这些产物也显示出明显的幻数特征。最后，我们报告的第一个观察到的（CH 4）n2+dications从甲烷团簇。二价阳离子的存活阈值n ≥70，与多电荷离子裂变的液滴模型符合得很好。此外，我们提出的证据表明，这些dications是由一个不寻常的两步机制，这是由电荷转移产生一价阳离子，然后由潘宁电离产生的dication启动。
The electron ionization of helium droplets doped with methane clusters is investigated for the first time using high‐resolution mass spectrometry. The dominant ion products ejected into the gas phase are the unprotonated (CH4)n+cluster ions along with the protonated ions, CH5+(CH4)n−1. The mass spectra show clear evidence for magic numbers, which are broadly consistent with icosahedral shell closings. However, unusual features were observed, including different magic numbers for CH5+(CH4)n−1(n=55, 148) when compared to (CH4)n+(n=54, 147). Possible interpretations for some of these differences are proposed. Products of the type [C2Hx(CH4)n]+, which result from ion–molecule chemistry, are also observed and these too show clear magic number features. Finally, we report the first observation of (CH4)n2+dications from methane clusters. The threshold for dication survival occurs atn≥70 and is in good agreement with a liquid droplet model for fission of multiply charged ions. Furthermore, we present evidence showing that these dications are formed by an unusual two‐step mechanism which is initiated by charge transfer to generate a monocation and is then followed by Penning ionization to generate a dication.