Multitechnique investigation of the physisorption and thermal treatment of mixed-metal clusters on carbon

The three clusters [Ru6PtC(CO)16(COD)] (1), [Ru5PtC(CO)14(COD)] (2) (COD = 1,5-cyclooctadiene), and (NEt4)2[Pd6Ru6(CO)24] (3) were physisorbed onto an active carbon support and used as molecular precursors for supported particles. The samples before and after thermal treatment at 300 degrees C were characterized by a combination of SIMS, XPS, SEM and XRD. It was found that the clusters are molecularly intact, but present in the form of agglomerates on the support at the end of the physisorption step. After thermal treatment, the ligands were lost in all cases, leaving on the surface bimetallic particles containing both starting metals (Ru-Pt in the case of 1 and 2, and Ru-Pd in the case of 3). The presence of the counterion was evidenced for 3, before, but not after, heating. Molecular clusters are thus interesting precursors for the preparation of supported bimetallic phases, and SIMS is the ideal technique to characterize them at each step of their preparation.     

Neutral strange particle production in antineutrino-neon charged current interactions

Neutral strange particle production in \(\bar v\) Ne charged current interactions is studied using the bubble chamber BEBC, exposed to the CERN SPS antineutrino wide band beam. From a sample of 1191 neutral strange particles, the inclusive production rates are determined to be (15.7±0.8)% forK ⁰ mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for \(\bar \Lambda \) and (0.6±0.3)% for Σ⁰ hyperons. The inclusive production properties ofK ⁰ mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane.     

Production ofρ +, −, 0 (770),η(550), ω(783) andf 2(1270) mesons in\bar v neon and ν neon charged current interactions

The production of the meson resonances ?(770) (all three charge states), η(550), ω(783) andf ₂(1270) in \(\bar v\) Ne and ν Ne charged current interactions is investigated in a bubble chamber experiment with BEBC at CERN. Except for thef ₂, the main features of resonance production are reasonably well described by the Lund model, although the average resonance multiplicities are overestimated by the model by (67±30)%. The average multiplicities of all resonances, including thef ₂, are well reproduced by a semiempirical model, whose parameters were determined from hadron interaction data.