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Highly dispersed, unsupported Pt, Pd, Rh, and bimetallic R h P t and P t P d clusters were produced by laser ablation using a KrF excimer laser operating at power densities up to 1.9 GW/cm2. By the evaporation of two metals simultaneously, bimetallic clusters with variable stoichiometric composition were obtained, depending on buffer gas, buffer gas pressure, and the deposited laser energy. The ablation was carried out in a glass cell under a continuous gas flow or in a UHV system with a static gas atmosphere. The pressure ranged from 5 to 100 Torr. Emission spectra of the plasma plume were taken for detection of ions and highly excited atoms in order to study the temporal evolution of the ablation process. The expansion of the plasma plume was imaged with a CCD camera at different times after the laser pulse. In the first few nanoseconds, the expansion velocity reached values up to 3.5 x lo6 c d s . Characterization of the metal clusters by XPS showed that samples produced in the glass reactor are highly contaminated with carbon up to 60 atom %. However, by using a UHV system, the carbon content was reduced to 14 atom %. Alloy formation in bimetallic Rh/Pt particles with a l-to-1 atomic ratio of rhodium to platinum was verified by EXAFS spectroscopy. The coordination environment around platinum consists of both platinum and rhodium neighbors, 56 and 44 atom %, respectively, while rhodium appears to be coordinated predominantly to other rhodium atoms. These results are consistent with a bimetallic Rh/Pt cluster model whereby the cluster core is composed of rhodium atoms and the outer surface is formed by platinum atoms. Particle size and size distribution were analyzed by XRD, TEM, and BET isotherms. The particle diameters ranged from 2 to 20 nm, showing a linear dependence on buffer gas pressure and laser energy.

To date, various connection rerouting methods for connection-oriented mobile networks have been proposed. The previous methods, however, are limited to specific topologies or environments. In this paper, we propose the connection-information-based rerouting widely applicable to various connection-oriented mobile networks. This method requires neither a specific topology nor a complex connection, enables fast rerouting, provides appropriate route optimality, and can be extended easily.

The e n e w dependence of the cross section for production of doubly excited ridge states by inelastic electron scattering off atoms or ions is analysed within the framework of configuration interaction theory. Specifically, a pure two-electron system (He) is considered, and the partial width for the inverse process of autoionization from a doubly excited state 10 the ground state continuum is calculated. As in earlier analyses, we find that the cross section behaves as a -Np, where N denotes the doubly excited level. We determine the exponent to be p RZ -6.5, our analytical derivation of it being in good agreement with an actual numerical calculation of the relevant panial widths. This mult is to be compared to a similar WatmeN of the process using the group theoretical doubly excited symmetry basis (DESB) which yields p = -7.