ZnS doped with rare earth ions is an important luminescence material. But very few works have been done in finding their Judd-Ofelt parameters so far. The reasons are:(1) The solubility of rare earth in ZnS is so low that it is difficult to measure the absorption spectrum. The standard method to get s from the measured absorption spectrum is unavailable.(2) It is well known that rare earth ions form a variety of luminescence centers in ZnS. These centers may have different s and their spectra may sometimes overlap.Along with the progress in experimental technique and the gain of the knowledge about luminescence centers in ZnS:RE

these difficulties could be overcome at least for some rare earth ions.