Ionization potentials of niobium cluster oxides

Photoionization studies of transition metal clusters: Ionization potentials of ScnO (n=5−36)

“…A notable exception has been observed in a study of tantalum clusters, in which the IP of Tal~O was found to be nearly 0.5 eV lower than that of bare Tal~ [ 11 ]. Assuming, however, that scandium clusters behave similarly to niobium [10] and yttrium [41] clusters in this respect, then the ScnO IPs should provide a reasonable first order estimate for the corresponding bare cluster IPs. The IPs for S%O do not display the dramatic discontinuities and odd-even alternations displayed by clusters of the nearly-free electron metals such as the alkalis [13][14][15][16], aluminum [19] and coinage metals [17,18].…”

“…As for other transition metal cluster species which have been investigated, the largest IP variations occur among the smaller dusters, and decrease in magnitude with increasing cluster size. In recent photoionization of niobium cluster oxides Nb,O m [10] and yttrium cluster monoxides [41] it was found that in most cases, the IPs of clusters containing a single oxygen atom were not significantly different (generally < 0.2 eV) from those of the corresponding bare clusters. A notable exception has been observed in a study of tantalum clusters, in which the IP of Tal~O was found to be nearly 0.5 eV lower than that of bare Tal~ [ 11 ].…”

“…These studies are motivated in large part by the relevance of such species to heterogeneous catalysis and have significantly added to our knowledge of the development of bulk metallic behavior starting at the microscopic limit. For example, threshold photoionization experiments have shown that the ionization potentials (IPs) of isolated V~ [2], Fe, [3][4][5], Co,, [5], Ni, [6,7], Nb, [8][9][10], and Tan [11] clusters display significant oscillations with cluster nuclearity n. Transition metal clusters do not, however, display the pronounced odd-even oscillations or "magic numbers" as are reflected in the IPs of alkali [12][13][14][15][16], coinage metal [ 17,18] and aluminum [19] clusters. In addition, these studies have shown that the size variation of transition metal cluster IPs deviate significantly from the predictions of the conducting spherical drop (CSD) model, which provides a classical size correction to the "work function" expected for small, spherical metallic particles [20][21][22][23].…”

Onset of carbon–carbon bonding in the Nb5Cy(y = 0–6) clusters: a threshold photo-ionisation and density functional theory study

“…As a check, the IPs extracted for Nb 5 and Nb 5 C 2 are found to be in good agreement with those previously determined. 22,28,29 For the Nb 5 C y series, relative to the IP of Nb 5 , addition of one C atom to Nb 5 only slightly reduces the IP (À0.13 eV). However, addition of two and three C atoms cause significant IP reductions of À0.86 and À0.88 eV, respectively.…”

Isomer selective infrared spectroscopy of neutral metal clusters

“…The cluster complexes are detected in a time-of-flight mass spectrometer after ionization with either an ArF excimer laser ͑6.42 eV/ photon͒ or a frequency-doubled dye laser. As the ionization potentials ͑IPs͒ for niobium clusters are typically in the 4.6-5.5 eV range 20,21 and as the IPs of their Ar complexes will be slightly lower, the 6.42 eV photon energy allows for one photon ionization of all clusters and their Ar complexes. The fluence of the ArF laser is kept sufficiently low to prevent absorption of multiple UV photons that would lead to fragmentation of the weakly bound complexes.…”