We have used digital video microscopy to study the equilibrium structure of quasi-two-dimensional suspensions of sterically stabilized uncharged polymethylmethacrylate spheres. Our experiments reveal the existence of an equilibrium hexatic phase as well as strongly first-order liquid-to-hexatic and hexatic-to-solid phase transitions. These observations are in agreement with the predictions of Bladon and Frenkel [Phys. Rev. Lett. 74, 2519 (1995)] for a confined colloid suspension in which the pair interaction potential between particles has a hard core and either a very short range attraction or a very short range step repulsion.

• Received 8 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.2577