A. Nakajima

Photoelectron spectroscopy of (C6F6)−n and (Au-C6F6)− clusters

Abstract Photoelectron spectra of hexafluorobenzene (C 6 F 6 ) cluster anions and its Au complex anion were measured in the gas phase at the photon energy of 3.49 eV, using a magnetic bottle electron spectrometer having ≈ 80 meV resolution. The spectra show unresolved broad features: The vertical detachment energies (VDEs) were determined from the maxima of the spectra. The VDE of (C 6 F 6 ) − n gradually increases by 0.1–0.2 eV with the cluster size ( n =1–8) from 1.56(3) to 2.54(6) eV, and the VDE of (Au-C 6 F 6 ) − anion is 1.99(5) eV.

Photoelectron spectroscopy of germanium-fluorine binary cluster anions: the HOMO-LUMO gap estimation of Gen clusters

Abstract Electronic properties of germanium-fluorine cluster anions (Ge n F n − ; n =1–11, m =1–3) were studied using photoelectron spectroscopy (PES) with a magnetic-bottle type electron spectrometer. Compared between the PES of Ge n F − and those of the Ge n − , it was found that the dope F atom in Ge n F − deprives each Ge n − cluster of excess electron without any serious rearrangement of the Ge n framework. The F doping method enables us to estimate the HOMO-LUMO gap of the corresponding neutral Ge n clusters ( n =4–11). For a diatomic GeF − cluster, furthermore, the vibrational structures could be resolved to determine its vibrational frequency.

Production of jet-cooled coronene and coronene cluster anions and their study with photoelectron spectroscopy

Abstract Anions of coronene (C 24 H 12 ) and its clusters are produced by laser ablation of a pressed pellet sample in a double rod, pulsed nozzle source. Coronene anions are produced efficiently only when transition metal vapor is present in the same plasma from co-vaporization of a metal sample. Anion monomers and clusters of coronene are size-selected and studied with photoelectron spectroscopy in a magnetic bottle spectrometer. Spectra at 532, 355 and 266 nm probe electron affinities and neutral electronic states. The electron affinity of coronene is 0.47±0.09 eV and that of coronene dimer is 0.67±0.09 eV.

Electronic and geometric properties of exohedral sodium- and gold-fullerenes

The electronic and geometric properties of gas-phase exohedral C60NaN−, C70NaN−, and C60AuN− cluster anions are investigated. Time-of-flight mass spectrometry and photoelectron spectroscopy (PES) reveal complex-specific arrangements of the sodium and the gold atoms on the fullerene cage. The electron affinity of C60AuN clearly shows even–odd alternation with the number of Au atoms, which suggests a “dry” structure where Au atoms aggregate as a cluster on the C60. In contrast, C60NaN and C70NaN show a “wet” structure having the Na atoms packed into stable trimers on the surface. For C60NaN (N=0 to 4), PES experiments at a high photodetachment energy (5.81 eV) allow us to deduce the net charge transferred from the sodium atoms to the lowest unoccupied molecular orbital of the fullerene. For larger C60NaN, moreover, a metallic transition is shown to occur at N∼13, and analysis of the adiabatic electron affinity variations allows the identification of the first magic sizes corresponding to electronic shell cl...

Reactivity of positively charged cobalt cluster ions with CH4, N2, H2, C2H4, and C2H2

Reactivity of positively charged cobalt cluster ions (Con+,n=2−22), produce by laser vaporization, with various gas samples (CH4, N2, H2, C2H4, and C2H2) were systematically investigated by using a fast-flow reactor. The reactivity of Con+ with the various gas samples is qualitatively consistent with the adsorption rate of the gas to cobalt metal surfaces. Con+ highly reacts with C2H2 as characterized by the adsorption rate to metal surfaces, and it indicates no size dependence. In contrast, the reactions of Con+ with the other gas samples indicate a similar cluster size dependence; atn=4, 5, and 10−15, Con+ highly reacts. The difference can be explained by the amount of the activation energy for chemisorption reaction. Compared with neutral cobalt clusters, the size dependence is almost similar except for Co4+ and Co5+. The reactivity enhancement of Co4+ and Co5+ indicates that the cobalt cluster ions are presumed to have an active site for chemisorption atn=4 and 5, induced by the influence of positive charge.

Sodium doped binary clusters I: Ionization potentials of SinNam clusters

Sodium doped silicon clusters (SinNam, 3≤n≤11, 1≤m≤4) were produced by two independent laser vaporization methods and their ionization potentials were measured by scanning the wavelength of the UV dye laser. The IPs of most SinNam clusters decrease monotonously with the number of Na atoms, but IPs of Si7Nam and Si10Nam clusters show an apparent even-odd alternation; odd numbers of Na atoms efficiently decrease the IP but even numbers of Na atoms never significantly decrease the IPs. In addition, the reactivity of SinNam clusters for NO molecules was investigated with a fast flow reactor, and an anti-correlation between IP and the reactivity was clearly observed; clusters having high IP show low reactivity andvice versa.

Photoelectron spectra of small nanophase W metal cluster anions

Abstract We have recorded photoelectron spectra of W n − ( n =20–90) using a magnetic bottle type photoelectron spectrometer. Each photoelectron spectrum consists of a single, broad peak, shifted successively towards a higher electron binding energy (EBE) with increasing n . We estimated the threshold EBEs from the spectra. The threshold EBE versus n −1/3 plot showed a straight line and was extrapolated to 4.50 eV which is consistent with the W bulk work function, 4.55 eV. We also estimated the bond dissociation energies of W n − cluster anions using a simple energetic model.

Sodium doped binary clusters II: Electron shell of InnNam and AunNam clusters

Sodium doped binary clusters of indium and gold were produced by a laser vaporization method using two independent lasers. Photoionization efficiency spectra of these binary clusters were measured. The ionization potentials thus determined indicate the occurrence of the electron shell structure in these binary clusters.

Electronic Structure and Reactivity of Bimetallic Clusters Containing Sodium Atoms

Ionization potentials of Aln Nam , and Con Nam were measured. Appreciable decrease in the Ip value was observed as a general tendency when Na atoms are doped to the Al or Co clusters. In Al-Na systems, Ip increases when the total number of electrons satisfies the electronic shell closing. Reactivity change toward hydrogen adsorption was found to have nothing to do with the behaviors of the change in the ionization potentials of Con Nam.

Magic Numbers of Bimetallic Cluster Ions Consisting of Group-III Metals: The Icosahedric 13 Atom Clusters

Bimetallic negative cluster ions consisting of group-III metals (In, Al, and B) were generated by two independent laser-vaporization sources. Icosahedron structure consisting of 13 atoms could be ascertained by their magic numbers of In12A1 1 - and A112B 1 -