Proposed distributed feedback crystal cavities for x-ray lasers.

The strong interest in the coherent generation and guiding of x rays is well known. Many papers have recently appeared treating different concepts of stimulated x-ray emissions, 1-3 and x-ray guiding in thin films was achieved. 4 Crystals were suggested as end reflectors to generate feedback.' Here we suggest a different type of cavity using zeolite crystals that would guide the emitted x-rays and at the same time generate the necessary feedback for self-sustained oscillation. Zeolite crystals5-7 are aluminosilicate porous structures, commonly termed molecular sieves, with one-, two-, or three-dimensional channels having minimum pore diameters of 3-12 A. These channels are formed by the juncture of larger sodalite cage units that are arranged with a peri-