In-situ monitoring of room temperature reactions of lanthanides with nitrogen and hydrogen at low pressures

The dissociative chemisorption of molecular nitrogen on clean lanthanide surfaces at ambient temperature and low pressure is explored. In-situ conductance measurements track the conversion from the lanthanide metals to the insulating lanthanide nitrides. A small partial pressure of oxygen ($sim 10^{-8}$ mbar) is shown to inhibit the nitridation of lanthanides at $10^{-4}$ mbar of N$_2$. The rate of nitridation as a function of nitrogen pressure is measured at low pressure for a series of lanthanide elements, gadolinium, terbium, dysprosium, ytterbium and praseodymium. Exposure of the lanthanide surfaces to both N$_2$ and H$_2$ results in the formation of NH$_3$.