Electron Temperatures and Atom Formation in near-threshold Photoionized Magnetized Ultracold Neutral Plasmas

In ultracold neutral plasmas (UNPs), three-body recombination is predicted to be the primary limitation to achieving the coldest possible electron temperatures. This limits the study of plasma physics in these systems, particularly with respect to studies of strong coupling and correlations in the electron component of UNPs. Magnetic fields are predicted to reduce the recombination rate which should in turn allow for lower electron temperatures. We have experimentally measured the atom population in UNPs formed through photoionization near the ionization threshold such that the initial kinetic energy imparted to the free electron component of the UNPs is small. From comparing these measurements to molecular dynamics simulations of these UNPs the electron temperature at multiple magnetic fields can be determined and compared to predicted limits.