Although bare protonated methane is by now essentially understood at the level of intramolecular large-amplitude motion, scrambling dynamics and broadband vibrational spectra, the microsolvated species still offer plenty of challenges. One aspect is the effect of the attached solvent molecules on the infrared absorption spectra of microsolvated CH₅⁺ complexes compared to the bare parent molecule. In this study we analyze, based on ab initio molecular dynamics simulations, protonated methane molecules that have been microsolvated with up to three hydrogen molecules, i.e. CH₅⁺·(H₂)_n. In particular, upon introducing a novel multi-channel maximum entropy methodology described herein, we are able to decompose the infrared spectra of these weakly-bound complexes in the frequency window from 1000 to 4500 cm⁻¹ into additive single mode contributions. Detailed comparisons to the bare CH₅⁺ parent reveal that these perturbed modes encode distinct features that depend on the exact microsolvation pattern. Beyond the specific case, such understanding is relevant to assess tagging artifacts in vibrational spectra of parent molecules based on messenger predissociation action spectroscopy.

中文翻译：

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标记对微溶剂化质子化甲烷的中红外光谱的影响†

尽管目前基本上从分子内大振幅运动，加扰动力学和宽带振动光谱的水平上理解裸质子化的甲烷，但微溶剂化的物种仍然提出了许多挑战。一方面是与裸露的母体分子相比，附着的溶剂分子对微溶剂化CH ₅ ⁺配合物的红外吸收光谱的影响。在这项研究中，我们从头算分子动力学模拟出发，分析了质子化的甲烷分子，该分子已被最多三个氢分子（即CH ₅ ⁺ ·（H ₂）_n。特别地，在引入本文描述的新颖的多通道最大熵方法之后，我们能够将这些弱结合的络合物在1000至4500cm ^-1的频率窗口中的红外光谱分解成加法单模贡献。与裸CH ₅ ⁺母体的详细比较显示，这些扰动的模式编码依赖于精确微溶剂化模式的不同特征。除了特定的情况外，这种理解对于基于信使预离解作用光谱法评估母体分子振动光谱中的标记伪影也很重要。