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首页> 外文期刊>The Journal of Chemical Physics >Vibrational predissociation spectroscopy of the (H2O)(-)(6-21)clusters in the OH stretching region: Evolution of the excess electron-binding signature into the intermediate cluster size regime
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Vibrational predissociation spectroscopy of the (H2O)(-)(6-21)clusters in the OH stretching region: Evolution of the excess electron-binding signature into the intermediate cluster size regime

机译：OH拉伸区域中（H2O）（-）（6-21）团簇的振动预离解光谱：多余的电子结合签名演变为中间簇尺寸机制

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摘要

We report vibrational predissociation spectra of the (H2O)(n)(-) cluster ions in the OH stretching region to determine whether the spectral signature of the electron-binding motif identified in the smaller clusters [Hammer et al. Science 306, 675 (2004)] continues to be important in the intermediate size regime (n=7-21). This signature consists of a redshifted doublet that dominates the OH stretching region, and has been traced primarily to the excitation of a single water molecule residing in a double H-bond acceptor (AA) binding site, oriented with both of its H atoms pointing toward the excess electron cloud. Strong absorption near the characteristic AA doublet is found to persist in the spectra of the larger clusters, but the pattern evolves into a broadened triplet around n=11. A single free OH feature associated with dangling hydrogen atoms on the cluster surface is observed to emerge for n >= 15, in sharp contrast to the multiplet pattern of unbonded OH stretches displayed by the H+.(H2O)(n) clusters throughout the n=2-29 range. We also explore the vibration-electronic coupling associated with normal-mode displacements of the AA molecule that most strongly interact with the excess electron. Specifically, electronic structure calculations on the hexamer anion indicate that displacement along the -OH2 symmetric stretching mode dramatically distorts the excess electron cloud, thus accounting for the anomalously large oscillator strength of the AA water stretching vibrations. We also discuss these vibronic interactions in the context of a possible relaxation mechanism for the excited electronic states involving the excess electron. (c) 2005 American Institute of Physics.
机译：我们报告了OH拉伸区域中（H2O）（n）（-）簇离子的振动预离解谱，以确定在较小簇中是否确定了电子结合基序的光谱特征[Hammer等。 [Science 306，675（2004）]在中等规模研究中仍然很重要（n = 7-21）。此特征由主导OH拉伸区的红移双峰组成，并且主要追溯到位于双H键受体（AA）结合位点的单个水分子的激发，其两个H原子都指向多余的电子云。发现较大的团簇的光谱中持久存在特征AA双重峰附近的强吸收，但是该模式演变为在n = 11附近变宽的三重峰。在n> = 15时，观察到与簇表面上悬挂的氢原子相关的单个游离OH特征出现，与H +显示的未键合OH拉伸的多重态形成鲜明对比。（H2O）（n）簇贯穿n = 2-29范围。我们还探讨了与电子分子与过量电子最强烈相互作用的正常模式位移相关的振动电子耦合。具体而言，对六聚体阴离子的电子结构计算表明，沿-OH2对称拉伸模式的位移会极大地扭曲多余的电子云，从而解释了AA水拉伸振动异常大的振荡器强度。我们还将在涉及过量电子的激发电子态的可能弛豫机制的背景下讨论这些振动相互作用。 （c）2005年美国物理研究所。

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