Electromagnetically induced transparency and absorption due to optical and ground-state coherences in Li-6

We present an experimental study of sub-natural width resonances in fluorescence from a collimated beam of 6Li atoms excited on the D1 and D2 lines by a bichromatic laser field. We show that in addition to ground-state Zeeman coherence, coherent population oscillations between ground and excited states contribute to the sub-natural resonances. High-contrast resonances of electromagnetically induced transparency and electromagnetically induced absorption due to both effects, i.e., ground-state Zeeman coherence and coherent population oscillations, are observed