The simultaneous excitation of two electrons in atomic cadmium

Abstract
A new investigation of the Cd I absorption spectrum, with an electron synchrotron as a background continuum source, has revealed 110 new features between 400 and 1100 angstrom. The new lines are identified by comparison with Cd II energy levels, Hartree-Fock calculations and the Zn I absorption spectrum in the same energy region (Mansfield & Connerade 1978). All are attributable to simultaneous excitation of two electrons, observed for the first time in cadmium. At longer wavelengths the spectrum is due to the excitation of both valence electrons and at shorter wavelengths it is due to excitation of one valence, and one 4d-subshell electron. The detailed analysis suggests that, as in zinc, double-excitation occurs through a final state configuration mixing process similar to conjugate shake-up.