A new dual-target dual-laser vaporization source for the production of binary metallic clusters is presented. Clusters of the type AunXm (X=Al, Fe, Co, Ni) were produced. Excellent control over the mixing process was achieved by varying the delay time between the firing of the two lasers and their energy densities. Having identified these critical parameters, their influence over the production process is shown in detail for the AunAlm system. The production of bimetallic clusters in this source is due to the spatial and temporal overlap of the two laser vaporized materials in the source.

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We report on experimental and theoretical investigations of the ionization potentials and structures of lithium monoxide clusters. The clusters were produced by a laser vaporization source, laser ionized, and mass selected by a time-of-flight mass spectrometer. Threshold photoionization spectroscopy was performed using photon energies of 3–5.52 eV and 6.4 eV. Ionization potentials of LinO (2⩽n⩽70) were derived from the photoionization efficiency curves. The evolution of the ionization potentials as a function of cluster size shows distinct steps at n=10, 22, and 42, and a pronounced odd–even staggering up to n≈42. These steps are in agreement with the shell model for metallic clusters, provided that the oxygen atom localizes two of the lithium valence electrons while leaving the other valence electrons delocalized in a metallic cluster. For the small clusters (n<6), fine structure is observed in the threshold spectra, possibly due to the presence of isomeric states in the cluster beam. Geometries and relative stabilities of the smaller LinO clusters (2⩽n⩽8) were computed by means of density functional theory using the B3LYP functional, and adiabatic and vertical ionization potentials were calculated. A comparison with the experimental ionization potentials provides evidence for the greater importance of rigid geometrical structures over metal-like characteristics for the small clusters.

First results obtained with a new type of on-line laser ion source based on resonant photoionization in a buffer gas cell are presented. The main advantages of this new target-ion-source system are its high efficiency, its selectivity, its short delay time, and its universality. This is demonstrated with the production of an isotopically and isobarically pure beam of "Ni (T~/2 = 200 ms).PACS numbers: 29.25.NiAlready during the first conference on nuclei far from stability dealing with the question "Why and how should we investigate nuclides far off the stability line" (Lysekil, 1966 [1]), it was realized that on-line mass separators are

The population partition of metastable atoms after ion beam sputtering of polycrystalline Ni was studied. Resonant multiphoton ionization using double resonant two-color two-step photoionization was used. This allows the quantitative measurement of the relative population of all metastable states. The high lying metastable states with excitation energies around 2 eV show populations of the order of 10% of the ground state population which is several orders of magnitude higher than expected. The anomalous population partition is interpreted in the resonant electron tunneling model. [S0031-9007(96)02032-7] PACS numbers: 79.20. Rf, 32.80.Fb, 32.80.Rm The fundamental physical processes governing ion beam sputtering can be studied experimentally by examining the ejected particles. The inelastic collisions of energetic ions with solid surfaces result in the ejection of atoms or clusters in different charge states and in different states of electronic excitation. Both the experimental and theoretical situations have been reviewed by Yu [1]. It is generally assumed that the fraction of sputtered atoms on highly excited metastable states is very low [2][3][4]. This assumption is based on quasithermal excitation and nonradiative deexcitation which depend strongly on the excitation energy.However, theoretical models and, albeit scarce, experimental evidence for a substantial population of such states are available. Indeed, the electron transfer model of Veje [5] predicts strong population of all states within an atomic excitation energy window corresponding to the valence band of the solid under study. Experimentally, in a study of Fe atom sputtering using laser induced fluorescence, a considerable population of metastable states at about 1 eV excitation energy was observed [6,7]. Measurements based on fluorescent photon detection, however, suffer from limited sensitivity and can therefore not be generally applied.Recently, studies of population and kinetic energy distributions of sputtered metastable Ni atoms, using resonant ionization spectroscopy (RIS) [8], were reported [3,4]. However, the experimental procedure used in these investigations limited the study of metastable states to excitation energies below 0.5 eV. Also recently, RIS was applied to probe the population of one high lying metastable state of sputtered Ag atoms; a population of about 6% of the ground-state population was deduced from the data [9,10]. The observations on sputtered Ni and Ag were interpreted as evidence for the fact that the sputter yield of metastable atoms depends on the electronic structure of both the solid and the sputtered atom.In this Letter we report on the development and application of a very sensitive experimental procedure for the quantitative measurement of relative populations of all metastable states. The method is based on resonant multiphoton ionization spectroscopy using two-color twostep ionization schemes in combination with time-of-flight mass spectrometry. Application of this technique to the study of metastable N...