Direct Laser Cooling of Rydberg Atoms with an Isolated-Core Transition.

We propose a scheme to directly laser cool Rydberg atoms by laser cooling the residual ion core within the Rydberg-electron orbit. The scheme is detailed for alkaline-earth-metal Rydberg atoms, whose ions can be easily laser cooled. We demonstrate that a closed optical cooling cycle can be found despite the perturbations caused by the Rydberg electron and that this cycle can be driven over more than 100  μs to achieve laser cooling. The cooling dynamics with and without the presence of magnetic fields are discussed in detail.