Nitrogen Molecule Adsorption on Cationic Tantalum Clusters and Rhodium Clusters and Desorption from Their Nitride Clusters Studied by Thermal Desorption Spectrometry.
Adsorption and desorption of N2 molecules onto cationic Ta and Rh clusters in the gas phase were investigated in the temperature range of 300-1000 K by using thermal desorption spectrometry in combination with density functional theory (DFT) calculations. For Ta6(+), the first N2 molecule was found to adsorb dissociatively, and it remained adsorbed when Ta6(+)N2 was heated to 1000 K. In contrast, the second and the subsequent N2 molecules adsorbed weakly as a molecular form and were released into the gas phase when heated to 600 K. The difference can be explained in terms of the activation barrier between the molecular and dissociative forms. On the other hand, when Ta clusters were generated in the presence of N2 gas by the laser ablation of a Ta rod, isomeric clusters, TanNm(+), having heat resistivity were formed. For Rh6(+), N2 adsorbed molecularly at 300 K and desorbed totally at 450 K. These results were consistent with the DFT calculations, indicating that the dissociative adsorption of N2 is endothermic.
Nitrogen absorption and dissociation on small Tantalum clusters
Abstract Using a first-principles PAW based technique we study the absorption of N2 on small Tan ( n ≤ 4 ) clusters and show that such clusters do dissociatively absorb N2 and are suitable candidates for catalysis in reactions which require dissociation of N2.
Anionic Oligomerization of Acrylonitrile Molecules Initiated by Intracluster Electron Transfer from Alkali Metal Atoms: Photoionization Mass Spectrometry of M(CH2CHCN)n (M = Li, Na, and K)
We investigated the photoionization mass spectrometry of clusters of alkali metal atoms (M = Li, Na and K) solvated with acrylonitrile (AN; CH2CHCN) molecules to obtain the information on size-dependent stability of the clusters. In the photoionization mass spectra of Mm(AN)n, strong ion signals were observed at M+(AN)3. The M+(AN)n (n = 6 and 9) ions were also clearly observed as magic numbers in the mass spectra of M = Na and K. By comparison with the mass spectrum of cluster ions formed by ion−molecule reactions in the cluster source, these magic numbers were found to be due to the stability of neutral clusters. These results are explained by the intracluster electron transfer from an alkali metal atom to AN molecules followed by anionic oligomerization. The results of the calculation for Na(AN) based on density functional theory also supports this consideration.