Post-collision interaction in electron impact excitation of the p6 outer subshell in Na, K, and Cs atoms

Abstract

The post-collision interaction (PCI) energy shift of lines resulting from the decay of the np5(n+1)s22P3/2 lowest autoionizing states has been measured in the ejected-electron spectra of Na, K, and Cs atoms. The data reveal several new features in the energy dependences of the line shift. Particularly, contrary to the smooth asymptotic character predicted by the known models of the PCI, the oscillations of the shift are observed in Na and K atoms. The oscillations appear in those energy regions where the strong negative-ion resonances are present in excitation functions for the np5(n+1)s22P3/2 states. Despite the strong resonance excitation of the 5p56s22P3/2 state in Cs atoms, the respective PCI shift satisfies the classical description of the effect.