On the outermost d-subshell absorption spectra of Ge I and Sn I

The quenching of single electron excitation channels first reported in the outermost d-subshell spectra of In I and Ga I is investigated here for the elements Sn I and Ge I. The absorption spectra of Sn I and Ge I between 320 and 1000 ŧ have been observed for the first time. Discrete structure is attributed to the excitation of a single electron from the outermost d-subshell and identifications of the upper configurations are obtained by comparison with Hartree-Fock calculations, the atomic structure being computed in approximate LS coupling. There is evidence that the 4d spectrum of Sn I is affected by the proximity of the double ionization threshold.