BUTCHER AND OEMLER CLUSTER A2111 - A HEAD-ON MERGER AT Z=0.23

We present ROSAT PSPC and HRI observations of A2111, the richest galax y cluster photometrically surveyed by Butcher & Oemler. The cluster co ntains a distinct comet-shaped X-ray subcomponent that appears hotter than the rest of the cluster. The galaxy and X-ray surface brightness distributions of the cluster show a similarly elongated morphology. Th ese results suggest that the cluster is undergoing a head-on subcluste r merger, This merger may also be responsible for the high fraction of gas-rich blue galaxies observed in the cluster, We have further detec ted a poor cluster along the merging ads and at a projected distance o f similar to 5 Mpc from A2111.