Abstract
We have investigated the 2 {sup 2}S{sub 1/2}-4 {sup 2}S{sub 1/2} two-photon transition in atomic lithium by high resolution laser spectroscopy. The frequencies of the two-photon resonances have been measured with an accuracy of better than 1 MHz using a Fabry-Perot wavemeter. The centers of gravity of the 4 {sup 2}S{sub 1/2} levels are 35 012.033 582 (26) cm{sup -1} for {sup 7}Li and 35 011.544 497 (30) cm{sup -1} for {sup 6}Li. The transition isotope shift is 14 662.4 (10) MHz. We have also determined the magnetic hyperfine splitting constant for the 4 {sup 2}S{sub 1/2} state for both isotopes.