Charged Rare Gas Clusters

这个实验研究项目专注于在束流装置中产生的纳米级氦和其他稀有气体液滴的不同寻常的性质，包括由电子激发产生的纳米液滴的激发状态。用可变能量的电子轰击产生各种带电状态和亚稳态的液滴。这项拟议的工作建立在之前的一项观察基础上，即红外光可以产生电子的光分离，也可以产生亚稳态氦分子从星团中分离。将增加一台飞行时间速度分光仪，用于测量分离物种的能量分布。实验将测量(1)产生初始激发的轰击电子的能量，(2)分离所产生的驰豫粒子的光子的能量，以及(3)分离后这些粒子的速度分布。目标是了解团簇的态密度，测量捕获在气泡中的电子的基态动能，并研究团簇激子态的演化。这个实验研究项目探索了在束流装置中产生的纳米尺寸的稀有气体液滴的不同寻常的性质，特别是氦。特别令人感兴趣的是纳米级液滴与可变能量电子的相互作用，这使液滴进入能量改变和/或电荷改变的状态。由此产生的激发态是最重要的，并将利用光来探测，这已被发现导致亚稳态氦分子从激发团簇中分离。得到的光分离分子的速度分布将用飞行时间装置测量。这项研究将增加关于纳米级团簇的重要信息，它们与电子的相互作用，以及随着能量的提高它们状态的性质。这项研究项目本质上是跨学科的，涉及将接受良好培训以进入工业、政府或教育职位的研究生。***

w:\awards\awards96\num.doc 9705242 Northby This experimental research project focuses on unusual properties of nanometer scale droplets of helium and other rare gases, produced in a beam apparatus, including excited states of the nanodroplets produced by electron excitation. The bombardment with electrons of variable energy produces various charged and metastably excited states of the droplets. The proposed work builds on a previous observation that infrared light can produce photodetachment of electrons and also of metastable helium molecules from the clusters. A time of flight velocity spectrometer will be added and used to measure the energy distributions of the detached species. Experiments will be perfomed to measure (1) the energy of the bombarding electron which creates the initial excitation, (2) the energy of the photon which detaches the resulting relaxed particle, and (3) the velocity distribution of these particles after detachment. The goals are to learn about the cluster density of states, to measure the ground state kinetic energy of an electron trapped in a bubble, and to study the evolution of excitonic states of the cluster. %%% This experimental research project probes unusal properties of nanometer size droplets of rare gases, particularly helium, produced in a beam apparatus. Of particular interest are interactions of the nanometer scale droplets with electrons of variable energy, which put the drop into states of altered energy and/or altered charge. The excited states thus produced are of fundamental interest, and will be probed by use of light, which has been found to lead to detachment of metastable helium molecules from the excited clusters. The velocity distribution of resulting photodetached molecules will be measured with a time of flight apparatus. The research will add important information about nanometer scale clusters, their interactions with electrons, and the nature of their states as their energy is raised. This research project is interdisciplinary in nature and involves graduate students who will be excellently trained to enter positions in industry, government or education. ***