The quantum states in small, compact metal clusters are bunched into electronic shells with electronic orbitals resembling those in atoms, enabling classification of stable clusters as superatoms. The filling of superatomic orbitals, however, does not generally follow Hund's rule, and it has been proposed that magnetic superatoms can be stabilized by doping simple metal clusters with magnetic atoms. Here, we present evidence of the existence of a magnetic superatom and the determination of its spin moment. Our approach combines first principles studies with negative ion photoelectron experiments and enables a unique identification of the ground state and spin multiplicity. The studies indicate VNa 8 to be a magnetic superatom with a filled d-subshell and a magnetic moment of 5.0 μ B . Its low electron affinity is consistent with filled subshell and enhanced stability. The synthesis of this species opens the pathway to investigate the spin-dependent electronics of the new magnetic motifs.

Mass-selected, cluster anion beams of Mo100±2.5 – and (MoO3)67±1.5 – were prepared with a magnetron source and soft-landed onto highly ordered pyrolytic graphite (HOPG) under UHV conditions. These two clusters were selected because they possess essentially the same masses and consequently could be soft-landed with the same low kinetic energies. The chemical composition of the deposited clusters was analyzed using in situ Auger electron spectroscopy and ex situ X-ray photoelectron spectroscopy, while their surface morphologies were characterized with in situ scanning tunneling microscopy (STM) and ex situ atomic force microscopy (AFM). Both STM and AFM results indicated a high mobility for the metal atom clusters on HOPG at room temperature. At low coverages, Mo100±2.5 clusters nucleated preferentially at step-edges. As their coverage increased, cluster aggregates formed on the terraces until a fully saturated overlayer was created. By contrast, deposited metal oxide clusters produced a stochastic array of adsorbed clusters for all coverages. Differences in the behavior of deposited Mo100±2.5 and (MoO3)67±1.5 clusters were interpreted in terms of differences in the interactions of metal and metal oxide clusters with carbonaceous substrates.

Theoretical calculations based on density functional theory have found (PbS)(32) to be the smallest cubic cluster for which its inner (PbS)(4) core enjoys bulk-like coordination. Cubic (PbS)(32) is thus a "baby crystal," i.e., the smallest cluster, exhibiting sixfold coordination, that can be replicated to obtain the bulk crystal. The calculated dimensions of the (PbS)(32) cluster further provide a rubric for understanding the pattern of aggregation when (PbS)(32) clusters are deposited on a suitable surface, i.e., the formation of square and rectangular, crystalline nano-blocks with predictable dimensions. Experiments in which mass-selected (PbS)(32) clusters were soft-landed onto a highly ordered pyrolytic graphite surface and the resulting aggregates imaged by scanning tunneling microscopy provide evidence in direct support of the computational results.

The alanate anion, AlH4(-), was generated in the gas phase using a pulsed arc cluster ionization source. Its photoelectron spectrum was then measured with 193 nm photons. The spectrum consists of a broad feature, spanning electron binding energies from 3.8 eV to over 5.3 eV. This band reflects the photodetachment transitions between the ground state of the AlH4(-) anion and the ground state of its thermodynamically unstable neutral counterpart, AlH4. The vertical detachment energy (VDE) of AlH4(-) was measured to be 4.4 eV. Additionally, VDE values were also computed in a comprehensive theoretical study and compared both with the previously computed value and with our experimentally determined value.

A pulsed arc discharge source was used to prepare gas-phase, aluminum hydride cluster anions, Al(n)H(m) (-), exhibiting enhanced hydrogen content. The maximum number of hydrogen atoms in Al(n)H(m) (-) species was m=3n+1 for n=5-8, i.e., Al(n)H(3n+1) (-), and m=3n+2 for n=4, i.e., Al(4)H(14) (-), as observed in their mass spectra. These are the most hydrogen-rich aluminum hydrides to be observed thus far, transcending the 3:1 hydrogen-to-aluminum ratio in alane. Even more striking, ion intensities for Al(n)H(m) (-) species with m=3n+1 and m=3n+2 hydrogen atoms were significantly higher than those of nearby Al(n)H(m) (-) mass peaks for which m<3n+1, i.e., the ion intensities for Al(n)H(3n+1) (-) and for Al(4)H(14) (-) deviated from the roughly bell-shaped ion intensity patterns seen for most Al(n)H(m) (-) species, in which m ranges from 1 to 3n. Calculations based on density functional theory showed that Al(n)H(3n+1) (-) clusters have chain and/or double-ring polymeric structures.