Science Alliance Annual Report
2008–2009
UT-ORNL Distinguished Scientists
UTK physics and astronomy; ORNL physics
Joseph Macek
Atomic-scale systems
Since the early days of quantum mechanics, physicists have speculated about whether external forces might cause swirling electron vortices to appear inside simple atomic systems.
In 2007, theoretical physicist Joseph Macek discovered vortices could indeed be observed in the measurements of electrons ejected during impacts of charged particles or photoabsorption (a situation in which all of the energy of a photon is transferred to an atom, molecule, or nucleus).
Imagine the spinning, snaking vortex of a tornado. According to Macek’s three-dimensional representations, something like this happens when a proton punches its way into atomic hydrogen. A vortex forms as electrons move in response to the collision, leaving evidence of the original proton-hydrogen impact in their wake.
A search for experimental corroboration led the group to some unusual features observed in data from electron impact ionization (e,2e) processes—a technique used to ionize and fragment the sample molecules before analysis by mass spectroscopy.
The term e,2e is shorthand for the phenomenon that occurs when electrons strike an atom, molecule, or even a solid, and two electrons eject simultaneously. Observed both in computer simulation and experiments, these features have eluded explanation.
Macek says the atomic-scale vortices provide a likely explanation for these interesting structures. Detecting atomic-scale vortices in this context holds wide implications for the group’s discovery, since electron correlations are central to atomic, molecular, and condensed matter (solids) phenomena.
Experimental results support the group’s vortex theory. Studies probing electron correlations show circumstances where two electrons are completely absent from the atomic system; a situation which, in Macek’s calculations, corresponds to instances where there are zero measurable quantities.