## Far-infrared Rydberg-Rydberg transitions in a magnetic field: Deexcitation of antihydrogen atoms

The dynamics of (de)excitation between highly excited Rydberg states (15<n<60 of Rb) in a magnetic field of 0.85 {+-}0.05 T is studied with far-infrared pulses (90-110 and 50 {mu}m) originating from a free electron laser. We measured the excitation spectrum to states around n=40 from a deeper bound state near n=25. Moreover, starting from a highly excited state (30<n<60) below and in the n-mixing regime we investigated the efficiency of the deexcitation channel vs the ionization channel. We measured deexcitation efficiencies well above 50% for some of the states. However, starting deep in the n-mixing regime the deexcitation efficiency ismore »