New frontiers in X-ray photoionization of ions and atoms

A high-brightness tunable x-ray source, such as synchrotron, would be an extremely useful device for atomic physics studies. Since the coupling between the x-ray photons and the target is weak (of the order of the fine-structure constant, ∼ 1/137, compared to coulomb coupling), the dynamics of the target can be investigated. A high-brightness photon source is needed to produce enough counts to do an experiment in a finite time (where finite is related to the lifetime of the beam) where the target density is low. Target density may be low because it is difficult to create such a target, such as in the case of multi-charged positive ions. In addition, target density may be kept low intentionally, so that emerging electrons are not scattered on their way out of the interaction region before they are detected. Thus, a high-brightness x-ray synchrotron opens (or enhances) the possibility of a number of experiments concerning ions and atoms. In this paper, some of the emerging possibilities are outlined; it is meant to be indicative, not exhaustive