Whereas the xenon fluorides are well @-@ characterized , the other halides are not known , the only exception being the dichloride , XeCl2 . Xenon dichloride is reported to be an endothermic , colorless , crystalline compound that decompose into the elements at 80 ° C , formed by the high @-@ frequency irradiation of a mixture of xenon , fluorine , and silicon or carbon tetrachloride . However , doubt have been raised as to whether XeCl