A molecular beam of multilayer vanadium-benzene organometallic complexes Vn(C6H6)m was produced by a laser vaporization synthesis method. The magnetic moments of the complexes were measured by a molecular beam magnetic deflection technique, and were found to increase with the number of vanadium atoms in the cluster, showing that the unpaired electrons, which occupy the nonbonding dsigma orbitals localized on the metal atoms, couple ferromagnetically. These sandwich species represent a new class of one-dimensional molecular magnets in which the transition metal atoms are formally zerovalent.

Surfactant-free gold nanoparticles were prepared by laser ablation of a gold metal plate in water. The nanoparticles were characterized by absorption spectroscopy, ζ-potential measurements, and XPS spectroscopy. The nanoparticles are negatively charged because the surface atoms are partially oxidized to Au-O -, according to the literature by Sacher and co-workers (J. Phys. Chem. B, 2004, 108, 16864). We further examined electrostatic interactions between nanoparticle and cationic surfactants. It was found that the surfactant cations attach to the particle surface, neutralizing the particle charge. Taking advantage of the electrostatic interactions, we estimated that 3.3-6.6% of the surface gold atoms was oxidized in water.

A molecular beam of multilayer metal-benzene organometallic clusters Mn(C6H6)m (M = Al, Sc, Ti, and V) was produced by a laser vaporization synthesis method, and their magnetic deflections were measured. Multidecker sandwich clusters of transition-metal atoms and benzene Scn(C6H6)n+1 (n = 1, 2) and Vn(C6H6)n+1 (n = 1-4) possess magnetic moments that increase monotonously with n. The magnetic moments of Al(C6H6), Scn(C6H6)n+1, and Vn(C6H6)n+1 are smaller than that of their spin-only values as a result of intracluster spin relaxation, an effect that depends on the orbital angular momenta and bonding characters of the orbitals containing electron spin. While Ti(C6H6)2 was found to be nonmagnetic, Tin(C6H6)n+1 (n = 2, 3) possess nonzero magnetic moments. The mechanism of ferromagnetic spin ordering in M2(C6H6)3 (M = Sc, Ti, V) is discussed qualitatively in terms of molecular orbital analysis. These sandwich species represent a new class of one-dimensional molecular magnets in which the transition-metal atoms are formally zerovalent.

Gold nanoparticles exhibit optical absorption bands assignable to a broad interband in the UV region and a narrow intraband (surface plasmon band) in the 520 nm wavelength region. The gold nanoparticles were multiply ionized in an aqueous solution of sodium dodecyl sulfate when excited by a tightly focused nanosecond pulsed laser at 532 nm resonant to the intraband or at 355 nm resonant to the interband. Although the absorbance at 355 nm is almost comparable with the absorbance at 532 nm, gold nanoparticles with higher charge states were formed when the interband at 355 nm was excited. Our experimental findings and the theoretical prediction by Grua et al. (Phys. ReV. B 2003, 68, 035424) lead to the conclusion that electrons are predominantly released from the gold nanoparticles through thermionic emission by the excitation of the interband, whereas excitation of the surface plasmon band hardly contributes to the ionization processes.

The geometric and electronic structures of aluminum binary clusters, AlnX (X = Si and P), have been investigated, using mass spectrometry, anion photoelectron spectroscopy, photoionization spectroscopy, and theoretical calculations. Both experimental and theoretical results show that Al12Si has a high ionization energy and low electron affinity and Al12P has a low ionization energy, both with the icosahedral structure having a central Si or P atom, revealing that Al12Si and Al12P exhibit rare-gas-like and alkali superatoms, respectively. Experiments confirmed the possibility that the change in the total number of valence electrons on substitution could produce ionically bound binary superatom complexes, the binary cluster salts Al12P+ F- and Al12B- Cs+.

Transition metal (Sc, Ti, V, and Cr)-C 60 binary clusters were produced in the gas phase by a two-laser vaporization method. In the mass spectra of cationic M n (C 60 ) m + , for M ) Sc, Ti, and V, clusters having the composition of (n, m) ) (1, 1) + , (1, 2) + , (2, 3) + , (3, 4) + , (4, 4) + , and (5, 5) + were predominantly produced. The peaks having (n, n + 1) + compositions are explicable in terms of multiple dumbbell structures, in which metal atoms and C 60 are alternately stacked. Clusters with composition (4, 4) + and (5, 5) + are presumed to be ring structures. For Cr n (C 60 ) m + , however, a Cr atom is surrounded by three C 60 , forming a tricapped structure, and the structure acts as a unit for larger stable clusters of (2, 4) + , (3, 4) + , and (4, 4) + . Ionization energy measurements for neutral M n (C 60 ) m and a chemical probe method using CO, O 2 , and C 2 H 4 as reactants gave information concerning the geometrical and electronic structures.

Organometallic lanthanide complexes of Ln n (C8H8) m (Ln = lanthanide metals of Ce, Nd, Eu, Ho, and Yb; C8H8 = 1,3,5,7-cyclooctatetraene) were produced by a combination of laser vaporization and molecular beam methods. The complexes having (n, m) = (n, n + 1) for n = 1−5 were prominently produced as magic numbers in the mass spectra. Using mass spectrometry, photoionization spectroscopy, and photoelectron spectroscopy, it is concluded that these magic-numbered complexes form multiple decker sandwich structures in which Ln atoms and C8H8 molecules are alternately piled up. The obtained spectroscopic data show that these sandwich complexes are formed through ionic bonds and are charge transfer complexes, where the Ln atoms are multiply charged cations of Ln k + (k = 2 and 3) and C8H8 molecules are multiply charged anions.

Cerium oxide cluster ions, Ce(n)O(2n+x)(+) (n = 2-9, x = -1 to +2), were prepared in the gas phase by laser ablation of a cerium oxide rod in the presence of oxygen diluted in He as the carrier gas. The stable stoichiometry of the cluster ions was investigated using a mass spectrometer in combination with a newly developed post heating device. The oxygen-rich clusters, Ce(n)O(2n+x)(+) (x = 1, 2), were found to release oxygen molecules, and Ce(n)O(2n+x)(+) (x = -1, 0) were exclusively formed by post heating treatment at 573 K. The Ce(n)O(2n-1)(+) and Ce(n)O(2n)(+) clusters were found to be thermally stable, and the oxygen-rich clusters consisted of robust Ce(n)O(2n-1)(+) and Ce(n)O(2n)(+) and weakly bound oxygen atoms. Evaluation of the reactivity of Ce(n)O(2n+x)(+) with CO molecules demonstrated that Ce(n)O(2n)(+) oxidized CO to form Ce(n)O(2n-1)(+) and CO2, and the rate constants of the reaction were in the range of 10(-12)-10(-16) cm(3) s(-1). The CO oxidation reaction was distinct for n = 5, which occurred in parallel with the CO attachment reaction.