Satellite and hypersatellite structure of Mα_1,2 x‐ray transitions in thorium excited by fast oxygen ions

Abstract

The high‐resolution spectra of thorium Mα1,2 (M5 → N6,7) and Mβ1 (M4 → N6) x‐ray lines induced by an impact of O ions with energy 376.0 MeV were measured using a von Hamos crystal spectrometer in order to study the x‐ray emission from multiple ionized atoms. The observed x‐rays have been interpreted in terms of the relativistic multiconfiguration Dirac‐Fock (MCDF) calculations performed for dominating vacancy configurations expected to contribute to the measured spectra. Due to the complexity of such calculations for selected multi‐vacancy configurations the simplified average <MCDF> model, combining the MCDF calculations and binomial distribution of vacancies has been used. The measured spectra clearly exhibit a rich structure of Mα1,2 x‐ray satellites of thorium, including the transitions from the multivacancy initial configurations M−1N−n as well as the hypersatellites corresponding to the transitions in complex multivacancy initial configurations M−mN−n (m,n ≤ 4). The present interpretation of the measured satellite/hypersatellite structure of Mα1,2 (M5 → N6,7) x‐ray transitions allows us to determine the ionization probabilities for the M‐ and N‐shell in central collisions. The measured ionization probabilities are compared with the theoretical predictions of the geometrical model (GM), and the semiclassical approximation (SCA) using both the Dirac hydrogenic and Dirac‐Hartree‐Fock selfconsistent wave functions.