X-RAY EMISSION FROM RESONANT COHERENTLY EXCITED 290MEV/U AR17+ IONS CHANNELED IN CRYSTALS T.Azuma1), Y.Takabayashi2), T.Ito2), K.Komaki2), Y.Yamazaki2)3), S.Datz4), E.Takada5), T.Murakami5) 1) Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan 2) Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, Meguro, Tokyo 153-8902, Japan 3) Atomic Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan 4) Oak Ridge National Laboratory, Oak Ridge, Tenessee 37831-6377, US 5) National Institute of Radiological Sciences, Inage, Chiba 263-8555, Japan Resonant coherent excitataion of 1s electron to n=2 states in 390 MeV/u hydrogen-like Ar17+ions under planar channeling has been investigated through the observation of the subseqeunt two channels. The ionization from the excited states was monitored by the transmitted ions, and the radiative de-excitation was observed by the projectile K X-rays. The difference between charge-state and X-ray resonance profiles reflects the nature of n=2 levels, which are the mixed states of 2s, 2px, 2py and 2pz under the electric field of the crystal.