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

在晶体中流动的高能离子感受到周期性的振荡晶场。当这一周期对应的能量与离子内能级的激发能量匹配时，离子就有机会被共振激发，这通常被称为共振相干激发。我们用几十个GeV重离子成功地观测到了相干激发的高分辨光谱。由于能量高，获得了良好的相干性和非常尖锐的共振。我们尝试利用离子在沟道条件下的RCE这一独特的现象，对高电荷态离子进行高精度的原子光谱分析。我们开发了专门为目标晶体准备的硅探测器，用于测量晶体中的离子轨迹。利用这个探测器，我们同时测量了离子通过晶体的电荷分布和它们的沉积能量。在相同的束流条件下，观察到从基态到n=2，3，4能级的类氢Ar~(2+)&lt；17+&gt；离子的相干激发。通过这种方法，我们可以高精度地同时确定束流能量和跃迁能量，并推导出基态下的Lamb位移。也就是说，与n=2，3，4能级相比，基态下的Lamb位移要大得多。通过忽略激发态下的Lamb位移，从n=1，2，n=1，3，n=1，4之间的能量差出发，推导出基态Lamb位移和束流能量。前人尝试的类氢、类氦离子同时测量中产生歧义的主要因素，不仅是斯塔克效应的贡献，也是对束流条件的正确评价的困难，这与目前的测量形成了很好的对比。我们可以达到更高的精度，现在正在进行详细的分析。

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.