Laser Spectroscopy of Ions and Clusters

加州大学伯克利分校的Richard J. Saykally在实验物理化学项目的支持下，继续使用红外光谱对簇进行研究。目标是利用远红外（FIR）激光振动-旋转-隧道（VRT）光谱或红外腔环降激光吸收光谱（IR-CRLAS）确定水团簇（六聚体、八聚体和更大的）中的结构、力场和氢键网络重排。通过对二聚体光谱的分析，得到了水-水对势，并建立了较大的团簇和液态水的有效势。Saykally教授还将研究核苷酸碱基及其水合簇的分子间动力学。为了支持这些研究，一些技术进步正在计划中，包括将CRLAS进一步扩展到中红外，以及开发一种具有环形腔设计的新型FIR激光器。建立对液态水的详细和定量的了解仍然是一个重要的问题。虽然过冷水和疏水相互作用的有趣性质引起了许多著名化学家和物理学家的兴趣，但在广泛的温度范围内准确描述普通液体的更平凡的问题具有相当大的实际重要性。这个项目将提高我们对水的液体和固体相的理解，通过一次检查一个分子的连续较大的团簇，并使用新的激光技术和最先进的理论方法对这些团簇进行详细研究。所得数据最终将提供对液体中重要的许多身体力的更详细的描述。最新的研究成果涉及水与核苷酸碱基的氢键，显然在生物学上具有重要的基础意义。

Richard J. Saykally of the University of California in Berkeley is supported by the Experimental Physical Chemistry Program in his continuing studies of clusters using infrared spectroscopy. The goal is to determine structure, force fields and hydrogen bond network rearrangements in water clusters (hexamer, octamer and larger) using far infrared (FIR) laser vibration-rotation-tunneling (VRT) spectroscopy or infrared-cavity ring down laser absorption spectroscopy (IR-CRLAS). A water-water pair potential will be derived from analysis of the dimer spectra, and an effective potential for the larger clusters and liquid water will be constructed. Prof. Saykally will also investigate intermolecular dynamics of nucleotide bases and their hydrated clusters. To support these studies, a number of technological advances are planned including extension of the CRLAS deeper into the mid-IR and development of a new FIR laser with a ring cavity design. Establishing a detailed and quantitative understanding of liquid water continues to be a problem of major importance. While the intriguing properties of supercooled water and hydrophobic interactions occupy the interest of many prominent chemists and physicists, the more mundane problem of accurately describing the ordinary liquid over a wide range of temperatures is of considerable practical importance. This project will enhance our understanding of the liquid and solid phases of water by examining successively larger clusters one molecule at a time, and studying these clusters in great detail with new laser technology and state-of-the-art theoretical methods. The resulting data will ultimately provide a more detailed description of the important many body forces operating in the liquid. The newer effort involving studies of hydrogen bonding of water with nucleotide bases is clearly of fundamental significance in biology.