Sympathetic Cooling and Collisions of Atomic and Molecular Ions with Ultracold Atoms

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Sympathetic cooling of trapped atomic and molecular ions is investigated by using ion collisions with a second (ultracold) species of neutral atoms (e.g. sodium) which have previously been laser cooled to less than 1/1000th degree above absolute zero. This research focuses on very low energy ion-neutral atomic collisions as the cooling mechanism, about which very little is known experimentally. The boundaries of classical (Newtonian) and quantum (Schroedinger-Heisenberg) scattering are explored in new ways. The ion-neutral interaction under study is very general, involving the polarization (charge separation) of the neutral partner by the electric field of the ion; the polarized neutral atom then acts back to strongly attract the ion. Molecules (and molecular ions) are very difficult to laser cool directly, so this work should open up applications to general energy exchange processes in the solar system and interstellar space, control of ion-molecule exothermic reactions near zero Kelvin, generation of Wigner crystals of molecular ions in a lattice, precision spectroscopy of ions, ultraprecise atomic and molecular ion clocks, and potentially, quantum computers or quantum memory registers involving arrays of trapped ions. The project uses a special hybrid ion-neutral trap (MOT and Paul trap combination) to overlap clouds of alkali-metal atoms and various kinds of ions (e.g. Ca+, Na2+, Na+) and to allow observation of the rates of cooling and reactions that occur as a result. This basic research is relevant to atomic physics, molecular physics, frequency standards, space physics and astrophysics, quantum information and memories and their many applications. Atomic, molecular and optical physics (AMO) research at the University of Connecticut currently involves 10 active faculty and ~38 graduate students who receive a broad education involving all these areas, through their individual research, interaction with peers, weekly research seminars and colloquia, visits from scholars, public lectures and community outreach. Research results are frequently presented at conferences. One of the PI's students in undergraduate quantum mechanics for physics majors is now involved in PhD-level research on this project. Three undergraduate summer students, along with two exchange students from the University of Heidelberg have been involved. Undergraduates are encouraged to participate in related independent study projects. Students on the project receive a broad education in basic experimental physics techniques, including ultrahigh vacuum, laser cooling and trapping, optics, laser spectroscopy, ion manipulation and detection, etc.