Number 129 (Story #1), May 19, 1993 by Phillip F. Schewe and Ben Stein OPTICAL CRYSTALS are two- and three-dimensional ensembles of atoms held together not by inter-atomic forces but by beams of laser light. Gilbert Grynberg at the Pierre and Marie Curie University in Paris set up a standing-wave pattern using four lasers to position cooled (to microkelvin temperatures) cesium atoms in a cubic lattice array which persisted for about one second. Theodor Hansche and H. Hemmerich at the University of Munich have employed the same approach to fashion a two-dimensional lattice of cold rubidium atoms. Presenting their data at the Quantum Electronics and Laser Science Conference in Baltimore last week, both groups reported that the atoms in these "dilute solids" vibrated only at particular frequencies. (Science News, 15 May 1993.)