Two-Photon Absorption Experiment (IMAGE) University of California - Berkeley Caption A beam of hot barium atoms exits an oven and passes through a collimator before hitting overlapping laser beams. If photons sometimes act like fermions, every once in a while a barium atom would absorb two photons and subsequently emit a flash of light. No significant events were observed. Credit Damon English/UC Berkeley Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.