Ultrafast vibrational population dynamics of water and related systems: a theoretical perspective.
Ultrafast vibrational population dynamics of water and related systems: a theoretical perspective.
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DOI：
10.1021/cr020675f
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发表时间：
2004-02
期刊：
影响因子：
62.1
通讯作者：
R. Rey;K. B. Møller;J. Hynes
中科院分区：
文献类型：
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作者：
R. Rey;K. B. Møller;J. Hynes
由于非常明显的原因，科学家们长期以来一直对液态水着迷，因此，对这种特殊且特别重要的液体的微观理解的探索有着悠久而杰出的历史。[1]本综述的重点是近十年来液态水振动方面的快速进展，包括实验和理论方面的进展，这些进展是通过各种非线性超快红外和拉曼光谱方法进行探测的;对所涉及的一些实验技术的讨论可以在Elsaesser，[2] Bakker，[3]和Dlott的综述中找到。[4]鉴于作者的资格，基本观点是理论观点，但我们总是试图在实验的背景下讨论理论问题。水中的振动动力学可以大致分为两个重要的类别。在这篇综述中，我们专注于振动能量转移方面，即与人口的变化，例如，OH振动态的那些功能。第二类是关于“退相”或光谱扩散方面，也就是说，那些与调制的OH频率相关的功能，我们计划在一个单独的审查解决这个问题。我们需要开始几个重要的意见，确定我们讨论的范围和性质。第一点是需要注意的：事实上，我们的讨论虽然不是全部，但大部分都是关于在液态D2 O中稀释HOD的特殊水溶液体系，鉴于在该体系中OH伸缩的非常方便的孤立光谱特征，对这种水溶液体系进行了大量的实验研究。事实上，将这一系统称为“水”是一种滥用语言，尽管这是一种经常使用的语言。例如，正如Dlott及其同事所分类的，5 H2O和D2 O以及D2 O中的HOD在许多重要方面不同：液体D2 O是一种毒药，H2O分子中的键拉伸是耦合的，而HOD中的键拉伸不是，等等。这些差异应该始终记住，我们在不同的地方提请注意其中最重要的。第二点要注意的是，被探测分子参与的氢键（H键）6显然是我们讨论的核心（关于氢键系统中振动弛豫的早期模型研究，见参考文献7）。H键不仅是水溶液体系性质的重要组成部分，也是质子转移反应等基本化学溶液过程的关键（关于这种联系的最新综述，见参考文献8），并且是许多生物化学系统和过程的普遍方面。9.最后，我们需要指出的是，本简要审查报告是在非常紧张和迅速演变的事态发展中编写的，一些关键问题仍未解决。事实上，我们完全期望在不远的将来将需要进行另一次审查。尽管如此，我们希望目前的有限努力不会证明是徒劳的。
For quite obvious reasons, which need not be recounted here, scientists have long been fascinated by liquid water, and accordingly, the quest for a microscopic understanding of this special and especially important liquid has a long and distinguished history. 1 The focus of the present review is on the rapid progress within about the past decade, both experimental and theoretical, on the vibrational aspects of liquid water, as probed by nonlinear ultrafast infrared and Raman spectroscopic methods of various sorts; discussions of some of the experimental techniques involved can be found, for example, in the reviews by Elsaesser, 2 Bakker, 3 and Dlott. 4 In view of the qualifications of the authors, the underlying perspective is a theoretical one, but we attempt to always discuss theoretical issues in the context of experiments. Vibrational dynamics in water can be approximately divided into two important categories. In this review, we focus on vibrational energy transfer aspects, that is, those features associated with the change of population of, for example, OH vibrational states. The second category is concerned with “dephasing” or spectral diffusion aspects, that is, those features associated with modulation of the OH frequency; we plan to address this in a separate review. We need to begin with several important remarks defining the compass and character of our discussion. The first of these remarks is a caveat: in fact, much, though not all, of our discussion will concern the special aqueous system of HOD dilute in liquid D2O, an aqueous system much studied experimentally in view of the very convenient isolated spectroscopic feature of the OH stretch in this system, discussed within. In fact, it is an abuse of language, albeit one frequently practiced, to call this system “water”. As, for example, catalogued by Dlott and co-workers, 5 H2O and D2O and HOD in D2O differ in many important ways: liquid D2O is a poison, the bond stretches in the H2O molecule are coupled, while those in HOD are not, and so on. These differences should always be kept in mind, and we draw attention to the most important of them at various points within. A second remark is that the hydrogen bond (H bond) 6 in which the probed molecule participates obviously lies at the core of our discussion (for an early model investigation of vibrational relaxation in a hydrogen-bonded system, see ref 7). Not only is the H bond capital for the properties of aqueous systems, it is key for fundamental chemical solution processes such as proton-transfer reactions (for a recent review about this connection, see ref 8) and is a pervasive aspect of many biochemical systems and processes. 9 A final remark we need to make is that the present brief review is constructed in the midst of very intense and rapidly evolving developments, and a number of key issues remain unsettled. Indeed, we fully expect that another review will be required in the not-too-distant future. Nonetheless, we hope that the present limited effort will not prove to be inutile.