Spectral signatures of proton delocalization in H+(H2O)n=1-4 ions.
Spectral signatures of proton delocalization in H+(H2O)n=1-4 ions.
复制标题
H (H2O)n=1-4 离子中质子离域的光谱特征。
作者：
Laura C Dzugan;Ryan J DiRisio;L. Madison;A. McCoy
本文用几种理论方法研究了H ~+（H_2O）_n（n = 1-4）体系中涉及大振幅振动的耦合。这些包括谐波处理，谐波耦合非谐振子（HCAO）模型的OH伸缩振动，振动微扰理论（VPT 2）的内部坐标，扩散蒙特卡罗（DMC）的分析。据发现，共享质子拉伸和HOH弯曲之间的耦合可以导致正常模式，显着混合的字符。各种OH伸缩振动之间的耦合要弱得多，OH伸缩很好地描述了谐波耦合非谐振子模型。使用DMC和VPT 2进一步探讨了非谐耦合和这些大振幅振动的作用。基于这些计算的结果，它被发现，在这项研究中考虑的所有H+（H2O）n离子显示几种不同类型的大振幅振动运动，即使在它们的基态。在H7 O3+的情况下，简并VPT 2计算表明，共享质子伸缩和各种低频振动之间存在很大的耦合，这些振动对应于打破离子氢键的运动。这导致振动本征态具有来自几个零阶态的贡献。
Couplings involving large amplitude vibrations in H+(H2O)n (n = 1-4) are explored using several theoretical approaches. These include harmonic treatments, analysis of harmonically coupled anharmonic oscillator (HCAO) models of the OH stretching vibrations, vibrational perturbation theory (VPT2) in internal coordinates, and diffusion Monte Carlo (DMC). It is found that couplings between shared proton stretches and HOH bends can lead to normal modes that are significantly mixed in character. Couplings between the various OH stretching vibrations are much weaker, and the OH stretches are well-described by harmonically coupled anharmonic oscillator models. Anharmonic couplings and the role of these large amplitude vibrations are further explored using DMC and VPT2. Based on the results of these calculations, it is found that all of the H+(H2O)n ions considered in this study display several different types of large amplitude vibrational motions even in their ground states. In the case of H7O3+, degenerate VPT2 calculations indicate that there are large couplings between the shared proton stretch and various lower frequency vibrations that correspond to motions that break the ionic hydrogen bonds. This leads to vibrational eigenstates that have contributions from several zero-order states.