Precision spectroscopy of highly excited states in hydrogen atom

德国-俄罗斯联合项目旨在精确确定氢原子中2S-4P、2S-6P和2S-9P跃迁的光学频率。结合以前测量的1S-2S频率，这可以确定质子电荷半径和里德伯格常数。一个新的质子电荷半径的值具有重要意义，这是因为原子氢的测量结果与最近的Muonic氢的Lamb位移测量结果之间的差异。解决这个问题(质子电荷半径之谜)可能会得到更准确的里德堡常数值。我们计划设计新的超稳定激光系统来激发电偶极跃迁2S-4P、2S-6P和2S-10P，并测量目标不确定度小于3 kHz(光谱分辨率为1E12)的跃迁频率。为了达到与线宽的1E-4相对应的期望的不确定度，我们计划广泛地研究激发过程和系统效应，如多普勒效应、光泵浦、斯塔克漂移等。除了绝对测量跃迁频率的数目(2S1/2-4P1/2、3/2、2S1/2-6P1/2、3/2、2S1/2-9P1/2、3/2)外，还计划对系统频移的线形和贡献进行详细的理论研究。

Joint German-Russian project aims at precise determination of the optical frequencies of the 2S-4P, 2S-6P and 2S-9P transitions in atomic hydrogen. In combination with previously measured 1S-2S frequency this allows to determine the proton charge radius and the Rydberg constant. A new value for the proton charge radius is of significant importance due to discrepancy between measurements in atomic hydrogen and recent Lamb shift measurement in muonic hydrogen. Solving this (proton charge radius puzzle) may result in more accurate value for the Rydberg constant. We plan to design new ultra-stable laser systems for excitation of the electric dipole transitions 2S-4P, 2S-6P and 2S-10P and measure transition frequencies with a target uncertainty of less than 3 kHz (spectral resolution of 1E12). To reach the desired uncertainty corresponding to 1E-4 of the line width we plan to extensively study excitation process and systematic effects such as Doppler effect, optical pumping, Stark shift and others. Along with absolute measurements of the number of transition frequencies (2S1/2-4P1/2, 3/2, 2S1/2-6P1/2,3/2, 2S1/2-9P1/2, 3/2), a detailed theoretical study of the line shape and contributions of systematic frequency shifts is planned.