Abstract: Novel compositions of matter are disclosed having the general formula UO.sub.2 AA'L.sub.n, in which A and A' are anions whose conjugate acids have boiling points less than about 200.degree. C. and pK.sub.a values of 4.8 or less, L is a neutral ligand (1) having a boiling point of greater than about 200.degree. C. and an equilibrium constant for its exchange reaction with complexed tetrahydrofuran of greater than about 10.sup.-3, or (2) having an equilibrium constant for its exchange reaction with complexed tetrahydrofuran of greater than about 10.sup.3, and n is an integer of from 1 to 4.

Abstract: Processes are disclosed for the separation of isotopes of an element comprising vaporizing uranyl compounds having the formula (UO.sub.2 A.sub.2).sub.n, where A is a monovalent anion and n is an integer from 2 to 4, the compounds having an isotopically shifted infrared absorption spectrum associated with uranyl ions containing said element which is to be separated, and then irradiating the uranyl compound with infrared radiation which is preferentially absorbed by a molecular vibration of uranyl ions of the compound containing a predetermined isotope of that element so that excited molecules of the compound are provided which are enriched in the molecules of the compound containing that predetermined isotope, thus enabling separation of these excited molecules. The processes disclosed include separation of the excited molecules by irradiating under conditions such that the excited molecules dissociate, and also separating the excited molecules by a discrete separation step.