Projectile spectroscopy: a unification of average atom approach and detailed LSJ-split spectral distribution originating from complex autoionizing states

The analysis of the projectile effective charges and the stopping power with high intensity ion beams is of great fundamental interest. In contrast to the projectile charge state analysis outside the interaction volume (e.g., by means of particle detectors), the information about the projectile mean charge inside matter has to be obtained in an indirect manner, namely from the projectile radiation emission. The request for negligible absorption and observation of simultaneous several charge states leads to the analysis of the x-ray spectral distribution originating from complex autoionizing states. The possibility for the observation of these projectile X-ray spectral distributions inside matter was demonstrated recently [1]. Currently, however, there are no models available to transform the measured projectile spectral distribution into an average charge state inside matter. The complexity arises from the need for spectroscopic accuracy to interpret the spectral distribution. Whereas averaged atom models are powerful methods to treat the radiation physics of even complex atoms and ions [2], the averaging process by itself leads to an averaged spectral distribution too: