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. ***
