Scintillating Solutions Containing Heavy Elements

The use of heavy metals in scintillators (excited by high energy) is limited by two factors: 1) Such materials are very often not sufficiently soluble in solvents exhibiting considerable energy transfer, and 2) they generally quench the excitation energy of the solution and thereby decrease the fluorescent output. The latter effect was found to be due mostly to a quenching of the excited molecules of the solvent which are responsible for transferring energy, and to a lesser extent to the quenching of the fluorescent molecule, although this process also occurs. To circumvent the first difficulty one uses solvents with better solubilities for the metal compounds, but the choice is limited because of poor energy transfer characteristics of many of them. One of the best solvents found up to now is p-dioxane, which exhibits considerable energy transfer and shows better solubility properties than most of the other energy transferring solvents. Another means of overcoming difficulties of solubility is to use organic solvents favorable from the standpoint of solubility, but not so favorable from that of energy transfer. One can effectively induce considerable energy transfer in many of these solutions and thus produce high energy excited fluorescence by adding a relatively small amount, of the order of 10 per cent, of an effective liquid solvent (one which shows energy transfer).