Effect of electron correlations on the excitation of neutral states of zinc in the autoionizing region: A photon emission study

Electron impact excitation of the 4p0.2em0ex3,1P₁, 4d,5d,6d0.2em0ex³D1,2,3, and 4d,5d0.2em0ex¹D₁ states of the neutral zinc atom was studied by measuring photon decay intensities in the energy region of the 3d⁹4s²4p autoioionizing states. Two phenomena, both involving strong electron correlations and an active role of one of the $3d$ electrons in an intermediate scattering step, have been observed. The first is $3d$ core-excited negative-ion resonances, which dominate the energy region between 10.5 and 11.50.3em0exeV. The second is postcollision interaction (PCI) in the decay of autoionizing states which populates higher excited states at incident electron energies above 11.50.3em0exeV. The low energies of both the scattered and ejected electrons after near-threshold excitation of 3d⁹4s²4p autoionizing states enable a large transfer of orbital angular momentum, up to two units, by the PCI.