Bubbles form in liquid as a result of a number of different processes. They can be produced when the pressure on a liquid that contains gas is reduced, when a can of Coca Cola is opened, for example. Bubbles also form in the turbulence around the propeller of a ship or when a liquid is heated above its boiling point. In some situations, bubble production has undesirable effects. For example, over the course of time the bubbles produced near the propeller of a ship, damage the propeller. On the other hand, bubble generation can also be very useful, as in an ultrasonic cleaner. The long-range goal of this research is the study of how bubbles are formed and how to control the formation for technological advantage. Experiments will be performed to investigate bubble production in liquid helium under a number of different conditions. Liquid helium is chosen for these experiments because it can be produced with exceptional purity, and so effects that might arise from impurities in the liquid can be controlled or eliminated. The research project will contribute to the national need for scientists trained in the technically important fields of optics, cryogenics, fluid mechanics and computer simulation.
An electron injected into liquid helium forces open a small cavity, producing an "electron bubble" of radius 2 nm. This individual investigator award supports research that includes several projects to study these bubbles and to use them to investigate the properties of quantized vortices. The first project will be to investigate the "exotic ions", electron bubbles of unknown structure that are smaller than normal bubbles. In a second project a study will be made of electron bubbles in which the electron has been optically excited to the 1D quantum state. The third project is to attach electron bubbles to quantized vortices and by imaging these electrons, study the motion of the vortices. This work is exciting because electron bubbles are unique quantum systems with a size and shape of the bubble determined by the quantum state of the electron. Their study can answer fundamental questions concerning the nature of the measurement process in quantum mechanics. The research is a combination of experiment and theory, and includes collaboration with groups in Paris and Barcelona. With the combination of these components, the research is an excellent means for the training of graduate students and undergraduates.
