STM images showing the diffusion of a single ad-dimer on a Si(001) surface at 475K. Note that the dimer diffuses across three rows through the movie. Following Brocks' notation, the ad-dimers orientation changes from that of a B-dimer on top of a row to that of a C-dimer between two rows (presumably it has an intermediate state of an A-dimer). For diagrams of these and other dimer orientations, visit the gallery. There is a second ad-dimer in the lower left corner of the movie.Size= 256 × 256 Å Frame Rate= 1/4.6min. Click on the movie to stop the animation.