Resonant collisional energy transfer with Rydberg atoms

Resonant collisional energy transfer can be studied in uprecedented detail using Rydberg atoms. Using the dependence of the energy level spacing on principal quantum number it is possible to examine resonant energy transfer in collisions with molecules. Finer control of the level spacing is possible by varying the level spacings with an electric field. Using this approach it is possible to observe sharply resonant collisions between Rydberg atoms. They are resonant dipole-dipole collisions which have cross sections orders of magnitude larger than the geometric cross sections of the colliding Rydberg atoms. These collisions are interesting in themselves; for example, they exhibit intracollisional interference, and it is possible to know when individual collisions begin and end. Perhaps the most interesting aspect of these collisions is that, because of the large dipole moments of the Rydberg atoms, they are easily controlled by microwave and radio frequency fields