On the simultaneous excitation of two electrons in neutral atomic zinc

In a new investigation of the Zn i absorption spectrum between 400 and 1000 Å, 11 series due to the simultaneous excitation of two electrons have been observed for the first time in Zn i. At least 120 double excitations have been measured. They are identified by comparison with published Zn ii energy levels and with Hartree-Fock calculations. The new lines may be divided broadly into two groups, a longer wavelength group (900-990 Å) due to simultaneous excitation of the two valence electrons, and a shorter wavelength group (420-610 Å) due to simultaneous excitation of one valence and one sub valence subshell electron. A detailed examination of the two groups of two-electron transitions indicates that, in both cases, excitation occurs by a final state configuration mixing process related to conjugate shake-up.