HIGH PRECISION SPECTROSCOPY OF HIGHLY-CHARGED HEAVY IONS WITH USE OF RESONANT COHERENT EXCITATI

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High-energy ions channeled in a crystal feel the oscillating periodic crystal field. When the energy corresponding to this period matches with the excitation energy of the inner levels of the ions, the ions have a chance to be excited resonantly, which is often called as resonant coherent excitation. We have succeeded in observing well-resolved spectra of the coherent excitation with use of several tens GeV heavy ions. Owing to the high energy, good coherence and very sharp resonance are obtained. We tried high-precision atomic spectroscopy of highly charged ions taking an advantage of this unique phenomenon of RCE of the ions under the channeling condition.We developed specially prepared Si-detectors for target crystals to measure the ion trajectory in the crystal. Using this detector we simultaneously measured the charge distribution of the ions transmitting through the crystal, and their deposited energy. We observed the coherent excitation from the ground state to n=2,3,4 levels of H-like Ar^<17+> ions under the identical beam condition. In this manner, we could determine the beam energy and the transition energy at the same time with high precision, and deduce the Lamb shift in the ground state. That is, the Lamb shift is much larger in the ground state compared with those in the n=2,3,4 levels. By neglecting the Lamb shift in the excited state, we deduced the ground state Lamb shift and beam energy from the energy differences between n=1,2, n=1,3, n=1,4 difference. The major factors of the ambiguity in the simultaneous measurement of H-like and He-like ion, which had been previously tried, is not only the Stark effect contribution but also difficulty in the proper evaluation of the beam condition, which is good contrast to the present measurement. We could attain much better precision, and are now in the detailed analysis.