Laser induced two-step recombination for the study of Rydberg states in highly charged ions

Abstract Laser induced two-step recombination is used to populate Rydberg states in highly charged ions and to measure the fine structure of inter-Rydberg transitions. The experimental procedure employs photoionization in order to reduce the background due to one-photon recombination. In the spectrum for Rydberg levels of heliumlike C 4+ , transitions between low- l states are resolved. The signal due to the unresolved high- l states is possibly enhanced due to the mixing between the l levels in the radiation field at high laser intensities.