Observation of Ultra-narrow Electromagnetically Induced Transparency and   Slow Light using Purely Electronic Spins in a Hot Atomic Vapor
  Electromagnetically induced transparency (EIT) is observed in gaseous 4He at room temperature. Ultra-narrow (less than 10 kHz) EIT windows are obtained for the first time for purely electronic spins in the presence of Doppler broadening. The positive role of collisions is emphasized through measurements of the power dependence of the EIT resonance. Measurement of slow light opens up possible ways to applications. 
F. Goldfarb, J. Ghosh, M. David, J. Ruggiero, T. Chaneli\`ere, J.-L.   Le Gou\"et, H. Gilles, R. Ghosh, and F. Bretenaker