Matrix Isolation Infrared Studies of the Reactions of Laser-Ablated Uranium with N<INF>2</INF>:  Reactions beyond Insertion into N<INF>2</INF>

Uranium was laser-ablated in the presence of N<INF>2</INF>/Ar mixtures, and the reaction products were studied using matrix isolation infrared spectroscopy. These reactions were studied over a wide range of N<INF>2</INF> concentrations in Ar (0.1% to 50%) and also with pure N<INF>2</INF>. We observed that at low N<INF>2</INF> concentrations in Ar (&lt;1%), the reaction product was the insertion product UN<INF>2</INF> and its complexes with molecular N<INF>2</INF>, a result that agreed with an earlier report of Andrews and group. Interestingly, however, as the N<INF>2</INF> concentration was increased, we observed the formation of the mononitride, UN. We believe that as the N<INF>2</INF> concentration is increased, new reaction channels open up, resulting in the formation of nitrogen atoms and N<INF>3</INF> species which then react with laser-ablated uranium atoms to produce UN. The assignment of the infrared feature due to UN in a N<INF>2</INF> matrix is also discussed.