The H₆⁺ cation was generated in a pulsed-discharge supersonic expansion of hydrogen and mass-selected in a time-of-flight spectrometer. Its vibrational spectrum was measured in the region of 2050–4550 cm⁻¹ using infrared photodissociation with a tunable OPO/OPA laser system. The H₆⁺ photodissociates, producing H₅⁺, H₄⁺, and H₃⁺ fragments; each of these fragment channels has a different spectrum. Computational studies identify two low-lying isomers described in previous work, whose energies were evaluated at the CCSD(T)/cc-pVTZ//MP2/cc-pVTZ level of theory. A D_2d species having an H₂⁺ cation bridging between two perpendicular H₂ molecules is the global minimum structure. A C_s structure with an H₃⁺ core ion bound to both H₂ and an H atom lies 4.0 kcal mol⁻¹ higher in energy. Anharmonic vibrational spectra were computed for each of these isomers with second-order vibrational perturbation theory (VPT2) in combination with density functional theory at the B2PLYP/cc-pVTZ level. The comparison between experimental and predicted spectra confirms the presence of both the D_2d and C_s structures and explains the spectra in different fragmentation channels. Although we find reasonable agreement between the experiment and the spectra predicted by VPT2 computations, a more sophisticated computational approach is needed to better understand this complex system.

中文翻译：

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通讯：气相中H6 +阳离子的红外光解离光谱

H ₆ ⁺阳离子是在氢气的脉冲放电超声膨胀中产生的，并在飞行时间光谱仪中进行质量选择。使用可调谐OPO / OPA激光系统进行红外光解，在2050–4550 cm ^-1范围内测量了其振动光谱。H ₆ ⁺光解离，产生H ₅ ⁺，H ₄ ⁺和H ₃ ⁺片段；这些片段通道中的每一个都有不同的频谱。计算研究确定了先前工作中描述的两个低位异构体，其能量在CCSD（T）/ cc-pVTZ // MP2 / cc-pVTZ理论水平上进行了评估。A D _2d具有在两个垂直的H ₂分子之间桥接的H ₂ ⁺阳离子的物种是整体最小结构。具有结合到H ₂和H原子上的H ₃ ⁺核心离子的C _s结构的能量高4.0 kcal mol ^-1。利用二阶振动摄动理论（VPT2）结合密度泛函理论在B2PLYP / cc-pVTZ水平上针对这些异构体中的每一个计算了非谐振动光谱。实验光谱和预测光谱之间的比较证实了D _2d和C _s的存在构造和解释不同碎片通道中的光谱。尽管我们发现实验与通过VPT2计算预测的光谱之间存在合理的一致性，但仍需要一种更复杂的计算方法来更好地理解此复杂系统。