Abstract: Prof. Anne Goodsell

          Exciting Physics with Excited Atoms

          Physics and Astronomy Combined Colloquium   Friday, April 13th, 2012                                          2:30 PM to 3:30 PM  Thompson Physical Lab 205

Atoms can be excited by light beams, when the energy of each photon matches the energy for a particular atomic transition.  The resonant interaction between light and individual atoms in a gas can make those atoms heat up, cool down, or come to a nearly-complete stop in midair.  With the technique of laster cooling, we can slow atoms from speeds of hundreds of meters per second to just a few centimeters per second.  We are studying how electric fields can steer, manipulate, or capture these slow, laser-cooled atoms.  I will describe the results of our experiments at Harvard in which we have captured and ionized individual atoms interacting with the electric field of a single charged nanotube.  Looking toward the future, I will outline our plan for experiments at Middlebury to re-excite slow atoms and magnify the influence of external electric fields.  Slow atoms in a highly-excited state can be tremendously sensitive probes to investigate the strength of electric fields near the surface of a material.  As atoms in free flight move near a surface, their flight paths will be deflected by the force due to van der Waals attraction or by controlled fields near charged objects.  While an atom in the ground state is fairly insensitive to these disturbances, an excited atom can be significantly influenced by these small fields.