Molecules in Quantum Clusters: Structural and Dynamical Probes

这项研究项目得到了美国国家科学基金会理论和计算化学计划的支持，是对氢和氦团簇中的探测分子的研究。团簇的低激发声子态以及这些态与探测分子的振荡态的相互作用将用量子蒙特卡罗理论来处理。计算量包括探测分子如六氟化硫或双原子碘的寿命展宽、红外和拉曼光谱中的位移和分裂。通过比较理论和实验测量，可以确定主-主和主-杂质耦合，并用于研究量子流体中的其他能量耗散过程。这个项目的第二个主要组成部分是处理高能(1keV)电子从团簇中的散射，以研究电离和弹性散射截面。人们早就知道，由非常轻的原子或分子组成的液体(量子液体)，特别是氦原子或氢分子，表现出不寻常的性质，如超流动性。这个项目的主要目标是通过计算包含探测分子的小量子星团的实验可获得的光谱效应，来测试这些现象理论中的数学和理论方法。这一基本知识最直接的应用是超流体星系团的空间实验室实验理论，以及改进的低温火箭燃料的开发。

This research project, supported by the NSF Theoretical and Computational Chemistry Program, is a study of probe molecules in hydrogen and helium clusters. Low lying phonon states of the cluster and the interaction of these states with rovibrational states of a probe molecule will be treated by quantum Monte Carlo theory. Computed quantities include lifetime broadening, shifts and splittings in infrared and Raman spectra of probe molecules such as sulfurhexafluoride or diatomic iodine. By comparing theory with experimental measurements, the host-host and host-impurity couplings can be determined and used to study other energy dissipation processes in quantum fluids. A second major component of this project treats high energy (1 keV) electron scattering from clusters to study ionization and elastic scattering cross sections. It has long been known that liquids (quantum liquids) composed of very light atoms or molecules, particularly helium atoms or hydrogen molecules, exhibit unusual properties such as superfluidity. The principal goal of this project is to test mathematical and theoretical methods in the theory of these phenomena by computing experimentally accessible spectral effects on small quantum clusters containing probe molecules. The most immediate application of this fundamental knowledge is to the theory of spacelab experiments involving superfluid clusters, and to the development of improved cryogenic rocket fuels.