Electromagnetically induced absorption

A large increase in atomic absorption due to coherent interaction with resonant radiation is predicted for a closed transition between two degenerate atomic levels verifying $0l{F}_{g}l{F}_{e}{(F}_{g}$ and ${F}_{e}$ are the total angular momentum of the ground and the excited levels, respectively). In good agreement with the theoretical prediction, a total absorption enhancement by a factor 1.7 was obtained on the ${D}_{2}$ line of ${}^{85}\mathrm{Rb}\mathrm{}$ in a vapor cell experiment.