Action of different gases, specially nitrogen, on the formation of uranium clusters; comparison with niobium and tantalum clusters

We have studied the action of different gases like oxygen, nitrogen, hydrogen, on the formation of clusters of uranium, niobium and tantalum by high energy molecular bombardment. In the presence of oxygen we generally observe a decrease in the proportions of clusters of large masses, either with uranium or with niobium and tantalum. We observe the formation of many oxides with these last two metals. The action of nitrogen is particularly interesting with uranium, the total intensity of the formed clusters greatly increases; compounds of formulae: U p N q + with q ⩽ p + 1 are formed. In the case of niobium and tantalum the action is different; Nb p N +, Ta p N + and Nb p N 2 are formed; the proportion of these latter being very low. In the presence of hydrogen or deuterium few compounds are formed, either with uranium or the other two metals. We principally obtain X p H +, X p D + compounds, and the X 2H +, X 2D + compounds which are generally the most important. Hydrogen and deuterium do not modify the proportion of the different clusters.