Theoretical calculation for double K-shell vacancy production in lithium produced by fast charged projectiles

Full text: Electron transitions from the inner shell of lithium atom are very good examples for the importance of electron correlations in atomic transitions. It has been shown previously [1] that in case of single K-shell excitation experimental cross sections may be reproduced theoretically only if correlated wavefunctions are used for initial and final states. In the last years interesting experimental data have been published concerning to the single and double K-shell vacancy production in fast charged particle collisions [2,3]. In this work impact parameter calculations for double K-shell vacancy production in lithium are presented. In this case the system final state is a doubly excited Li+ ion and an electron in continuum. Theoretical results obtained with impact parameter method are compared with experimental data for 95 MeV/u Ar18+ [2,3], 60MeV/u Kr34+ and electron projectiles [4]. In first-order calculations correlation is included on description by the use of MCHF wavefunctions. In second-order calculations only the basic configurations are taken into account. The obtained results show good agreement with experimental data. The main mechanisms leading to the hollow Li+ ion and the effect of electroncorrelations are identified and analyzed in detail in case of S states. The dependence of cross sections on the projectile velocity and charge sign is also investigated