High-resolution study of the2sS3−2pP3transition inLi6,7II

The $2s{}_{}{}^3{}_{}{}^{}S-2p{}_{}{}^3{}_{}{}^{}P$ transition of ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$ II at 5485 Å, excited in a cooled hollow-cathode discharge, is observed in high resolution with a Hypeac interferometric spectrometer. Using separated isotopes, we have measured the absolute wavelengths of the 18 components of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ II and the 15 components of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ II. From these results we deduce (a) the hyperfine-structure constants for the ${}_{}{}^3{}_{}{}^{}S$ and ${}_{}{}^3{}_{}{}^{}P$ terms of both isotopes, (b) the fine-structure constants of the ${}_{}{}^3{}_{}{}^{}S$ term, and (c) the isotope shift and (d) the Lamb shift for the transition. Comparisons are made with recent many-body calculations and level-crossing and beam-foil experiments.