Resonant coherent excitation of heavy ions by crystal field

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Fast ions pissing through a single crystal feel periodically oscillating field.when they traverse atomic strings or atomic planes in the crystal, which is analogous to irradiation of virtual photon. When the energy of this oscillating field matches with the transition energy of the atom, the atom has a chance to be resonantly excited, which is called resonant coherent excitation (RCE).In the present experiments for RCE, we injected Ar or Fe ions of several 100 MeV/u accompanied with bound electrons in the ground state into a thin Si crystal. By employing a combination of a thin crystal of 1 m in thickness and high-energy, heavy ions, we suppressed ionization of the ion in the crystal and succeeded in observing RCE under the non-channeling conditions, where the ion s are excited by the array of specific atomic planes in the 3-dimensional crystal (3-dimensonal RCE: 3D-RCE).Utilizing 3)-RCE, we observed double resonance where two transitions take place simultaneously in the three level systems of lambda-type configuration of 11S, 21P and 21S of He-like Arm' ions. We found that the resonance profile splits into two separated peaks under the double resonance conditions. This characteristic feature results from the fact that the coupling field of 211) and 21S is intense enough to form the "dressed state". This situation is equivalent to the Autler-Townes doublet in quantum optics. In addition, through observation of the anisotropic emission yield of the de-excitation x-ray from the excited states by 3D-RCE, we could obtain the detailed information on the polarization of the oscillating filed.Thus, we conclude that we attained to get a unique and powerful tool for studying the coherent dynamics of the three-level system, which is equivalent to the irradiation both of a tunable X-ray and VUV lasers in synchronized operation.