Scattering by Strong Long-Range Forces, Quantum Superposition States of Nanoscale Objects: Exploring Quantum Rrocesses with the Use of Atomic Clusters

点击翻译按钮获取中文摘要

This research project employs the experimental techniques and capabilities of beams of mass-selected atomic nanoclusters to investigate two types of quantum phenomena, both of fundamental character but also of important practical significance. The first subject involves the influence of long-range potentials 'those of large permanent dipoles' on inelastic collisions. Specifically, absolute cross sections for electron capture by a very strong electric dipole field will be measured for the first time. In addition, the heretofore unexplored influence of a giant magnetic dipole on the capture process will be explored. Atomic clusters represent uniquely suitable targets for such measurements. The second part of the project will identify a novel quantum resonance existent at nanoscale dimensions: a cluster particle in a state corresponding to a quantum linear superposition of two geometric shapes. This identification will be accomplished via laser spectroscopy of free metal clusters with a well-defined size and isotopic composition. Optical spectroscopy of size-selected metal clusters exhibiting electronic shell structure (a.k.a. "artificial atoms") will be used to detect the influence of their isotopic mass on the collective electron resonance absorption. This peculiar isotope effect will reveal the presence of a novel quantum resonance phenomenon in the nanoscale domain: quantum superposition of cluster shape configurations.Atomic clusters are nanoscale aggregates made up of a finite number of atoms, from a few to thousands. They bridge the gap between individual atoms and molecules on one end, and larger particles (such as microstructures and aerosols) and bulk materials on the other. The ability to adjust precisely the cluster size and composition allows one to prepare quantum-size objects with useful and unusual features, and to investigate novel physical phenomena associated with these features. One property, utilized in this project, is the capability of certain clusters to generate extremely strong electric and magnetic fields in their vicinity, and to use these fields to attract and capture nearby charged particle, e.g. electrons. The project will measure the efficiency of this process, heretofore never explored for field intensities as high as those generated by the "polar" clusters. In addition to providing new fundamental insight, the results will have practical implications for understanding the interactions of ultracold molecules and ions, for the goal of achieving control of chemical reactions by externally applied fields, for investigation of magnetic nanoparticles, and for understanding processes occurring in atmospheric and interstellar environments. In the second part of the project, the ability of nanoclusters to execute quantum shape oscillations in other words, to be in a quantum superposition of two different shapes at the same time will be investigated. This experimental observation will reveal a new and distinctive case of quantum behavior appearing at the nanometer length scale. This research also has a strong conceptual overlap with nuclear physics and with the physics of ultracold atomic clouds, and may have applications in optical nanoelectronics. On the human resources side, the project will offer graduate students excellent training in a wide range of experimental and theoretical aspects of an inherently interdisciplinary field. Postdoctoral researchers will receive professional mentoring. Commitment to teaching and outreach includes ongoing active undergraduate student involvement in research, as well as contributions to university programs, science fairs, and workshops for domestic and international undergraduates.