ROLE OF D-SCREENING IN ION-EXCITED ELECTRON-EMISSION FROM CA

We report an analysis of the electron emission spectrum from Ca metal excited by rare-gas ion bombardment recorded at high-energy resolution . Energy considerations, assisted by electron-energy-loss measurements , indicate that the electron emission from Ca is dominated by the deca y of neutral excited atoms from 3p(5)3d4s2 states. The spectrum is exp lained in terms of initial 3p bombardment induced ionization followed by 3d neutralization as a result of d electron screening involving ele ctrons from the conduction band in the solid. On emerging from the sur face most Ca atoms are in the lowest 3p(5)3d4s(2) multiplets (P-3 and F-3)leading to electron emission via autoionization at energies well b elow that observed in resonant photoemission from Ca atoms. The result s give insight into the relationship between the d-screened core hole state in Ca and multiplets of core excited atomic states.