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

Abstract

Electron impact excitation of the $4p\phantom{\rule{0.2em}{0ex}}^{3,1}P_{1}$, $4d,5d,6d\phantom{\rule{0.2em}{0ex}}^{3}D_{1,2,3}$, and $4d,5d\phantom{\rule{0.2em}{0ex}}^{1}D_{1}$ states of the neutral zinc atom was studied by measuring photon decay intensities in the energy region of the $3{d}^{9}4{s}^{2}4p$ 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 $11.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The second is postcollision interaction (PCI) in the decay of autoionizing states which populates higher excited states at incident electron energies above $11.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The low energies of both the scattered and ejected electrons after near-threshold excitation of $3{d}^{9}4{s}^{2}4p$ autoionizing states enable a large transfer of orbital angular momentum, up to two units, by the PCI.