Spectoscopic Studies of Hydrogen Bonding in Size-and Conformation-Selected Biomolecule-(water)n Clusters

普渡大学的Timothy Zwier得到了实验研究的支持。 物理化学计划，研究氢键网络存在于 芳香族氨基酸-（水）n簇，在模型DNA碱基-（水）n 集群，并在模型DNA碱基对。 多种实验方法 将利用包括共振双光子电离（R2 PI），紫外-紫外 和红外-紫外烧孔光谱，共振离子浸渍红外光谱 光谱（RIDIRS）和腔衰荡光谱（CRDS）。 AB 为了比较的目的，还将进行初始计算， 以帮助光谱分配。 这是一个很长的一步，从一个孤立的单氢键在水中， 二聚体到液体中错综复杂的氢键网络 水和冰。 原因之一是H键 合作社 氢键的定量描述 两两相加的分子间势甚至不能解释 小气相团簇的最基本性质，更不用说体积 凝聚相 单个氢键的强度取决于 对氢键的数量、强度和方向敏感 在氢键网络中。 这种氢键的实验研究 网络充满了困难，主要是因为集群规模 增长，所以做的物种数量存在于样品中，掩盖了 单一物种的期望光谱。 需要更好的实验 探索是这些研究的主要动机。

Timothy Zwier of Purdue University is supported by the Experimental Physical Chemistry Program to study hydrogen bonding networks present in aromatic amino acid-(water)n clusters, in model DNA base-(water)n clusters, and in model DNA base pairs. A variety of experimental methods will be exploited including resonant two-photon ionization (R2PI), UV-UV and IR-UV hole-burning spectroscopies, resonant ion-dip infrared spectroscopy (RIDIRS) and cavity ring-down spectroscopy (CRDS). Ab initio calculations will also be carried out for comparison purposes and to aid in spectral assignment. It is a long step from an isolated single hydrogen bond in the water dimer to the intricate and complex hydrogen-bonded networks in liquid water and ice. One of the reasons is that H-bonds are strongly cooperative. Quantitative descriptions of the H-bonding using pairwise-additive intermolecular potentials fail to account for even the most basic properties of small gas-phase clusters, much less the bulk condensed phase. The strength of individual hydrogen bonds depends sensitively on the number, strength and orientation of the hydrogen bonds in the H-bonded network. The experimental study of such H-bonded networks is fraught with difficulty, largely because as the cluster size grows, so does the number of species present in the sample, masking the desired spectrum of a single species. The need for better experimental probes is the primary motivation for these studies.