One- and two-K-shell vacancy production in atomic Li by 95-MeV/u Ar18+ projectiles - art. no. 032715

Singly and doubly K-shell-vacant states in atomic Li, produced by 95-MeV/u Ar18+ projectiles, have been investigated. At this high velocity, excitatio n and ionization are expected to be well described by perturbation theories . High-resolution spectra for Auger electron emission, occurring in the ene rgy range similar to 50-90 eV and resulting from the deexcitation of singly or doubly excited states, were measured for various electron emission angl es. Both single-K-shell excitation and double-K-shell vacancy production sh ow strong dependences on the electron emission angle. Experimental anisotro py parameters for the P-2 states resulting from single-it-shell excitation are in good agreement with predictions of the Born approximation. In the ca se of double-K-shell-vacancy (i.e., hollow atom) production, the two it vac ancies are found to come about mainly by ionization plus excitation of the atomic Li target giving rise to excited states in Li+. Strong line intensit ies from the 2s(2) S-1 and 2s3s S-3 excited-state configurations are explai ned in terms of shake processes, providing direct spectral identification f or the electron-electron (e-e) interaction in producing the doubly vacant i t-shell configurations. Production of the 2s3s S-3 state, which has an inte nsity greater than that of the 2s(2) S-1 state, is attributed to a three-el ectron transition involving two shake transitions. Production of the 2s2p P -3 scare has a large contribution from the dielectronic manifestation of th e e-e interaction resulting from slow electron emission.