Spectroscopy of high Rydberg states of highly charged ions and antiprotonic helium atoms

We have performed fluorescence spectroscopy of high Rydberg states of highly charged ions (HCIs) extracted in vacuum using a microcapillary foil target. We identified photons emitted from ions with one electron in a high Rydberg state, for ∆n = 1 transitions from Q 1 n Q + 3 states in the VUV-visible-NIR light range. Timeresolved measurements clearly showed radiative cascade, and the initial population was deduced for the first time by our analysis which revealed that the electrons are preferentially transferred to states around n Q + 1, in good agreement with the classical over-barrier model. Also, laser spectroscopy of antiprotonic helium atom is introduced in the latter section to give a hint to the similar time-variant method for the aim of mapping the initial population, which gives an important information of atomic capture process of antiprotons.