The laser photoelectron spectra of ${\mathrm{Ge}}^{\mathrm{-}}$ and ${\mathrm{Sn}}^{\mathrm{-}}$ are reported. Transitions in the electron detachment from the ${}_{}{}^4{}_{}{}^{}\mathrm{S}_{3/2}^{}{}_{}{}^{}$ ground state of the ions to the ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$,1,2 states of the neutral atom are used to determine the electron affinities, 1.233±0.003 eV for Ge and 1.112±0.004 eV for Sn. The relative transition strengths to the fine-structure sublevels of the neutral do not follow the 1:3:5 statistical ratio, indicating the systematic breakdown of L-S coupling for these species.

• Received 28 October 1985

DOI:https://doi.org/10.1103/PhysRevA.33.3558