Cooperative two-photon absortion in a BEC of sodium atoms - Pedrozo-Peñafiel, E.; Castilho, Patricia Christina Marques; Mercado-Gutierrez, E. D.; Roati, G.; Farias, Kilvia Mayre; Bagnato, Vanderlei Salvador (Workshop on Collective Scattering of Light - CoScaLi, 2016)