Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
J Chem Phys. 2018 Jul 21;149(3):031105. doi: 10.1063/1.5043425.
The H 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 using infrared photodissociation with a tunable OPO/OPA laser system. The H photodissociates, producing H, H, and H 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 species having an H cation bridging between two perpendicular H molecules is the global minimum structure. A C structure with an H core ion bound to both H and an H atom lies 4.0 kcal mol 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 and C 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.
氢离子是在氢的脉冲放电超音速膨胀中产生的，并在飞行时间光谱仪中进行了时间选择。使用可调谐 OPO/OPA 激光系统进行红外光解，在 2050-4550cm 的区域测量了其振动光谱。氢离子光解，产生 H、H 和 H 碎片；这些碎片通道中的每一个都有不同的光谱。计算研究确定了之前工作中描述的两种低能异构体，其能量是在 CCSD(T)/cc-pVTZ//MP2/cc-pVTZ 理论水平上评估的。一种具有 H 阳离子桥接在两个垂直 H 分子之间的 D 物种是全局最小结构。一种具有 H 核离子与两个 H 和一个 H 原子结合的 C 结构的能量高出 4.0kcal/mol。用第二阶振动微扰理论 (VPT2) 结合密度泛函理论在 B2PLYP/cc-pVTZ 水平上计算了每个异构体的非谐振动光谱。实验和预测光谱之间的比较证实了 D 和 C 结构的存在，并解释了不同碎片通道中的光谱。尽管我们发现实验和 VPT2 计算预测的光谱之间存在合理的一致性，但需要更复杂的计算方法来更好地理解这个复杂的系统。
