Total cross section for hadron production by electron-positron annihilation at adone

The total cross section for electron-positron annihilation into three or more hadrons has been measured for centre of mass energies between 1.4 and 2.0 GeV. The data were obtained at ADONE by the BB? experiment.     

Excitation and emission enhancement of single molecule fluorescence through multiple surface-plasmon resonances on metal trimer nanoantennas

We study theoretically the light scattering from trimers of metal nanowires, with emphasis on the occurrence of multiple surface-plasmon resonances, showing that such resonances can be exploited to achieve twofold-enhanced fluorescence from a single molecule placed in the nanotrimer gaps, even if excitation and emission frequencies are separated. Pump enhancement stems from the local field enhancement coinciding with one of the resonances, whereas a strong enhancement of the radiative decay rate (and quantum yield) is revealed at a different resonance, leading to a large overall signal emission.     

Capping [H<Subscript>8−n</Subscript>Ni<Subscript>42</Subscript>C<Subscript>8</Subscript>(CO)<Subscript>44</Subscript>]<Superscript>n−</Superscript> (n = 6, 7, 8) Octa-carbide Carbonyl Nanoclusters with [Ni(CO)] and [CuCl] Fragments

The reactions of [Ni₁₆(C₂)₂(CO)₂₃]^4? and [Ni₃₈C₆(CO)₄₂]^6? with CuCl afforded mixtures of the previously reported [HNi₄₂C₈(CO)₄₄(CuCl)]^7? bimetallic octa-carbide cluster and the new [HNi₄₃C₈(CO)₄₅]^7? and [HNi₄₄C₈(CO)₄₆]^7? homo-metallic octa-carbides. The three species have very similar properties resulting always in co-crystals such as [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·6.5MeCN (x = 0.14) (86% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 14%[HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?) and [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·5.5MeCN (x = 0.30) (70% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 30% [HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?). The new homo-metallic octa-carbides can be obtained free from the Ni–Cu octa-carbido cluster by reacting [Ni₁₀(C₂)(CO)₁₆]^2? in thf with a stoichiometric amount of CuCl, and crystals of [NMe₄]₆[H₂Ni_43+xC₈(CO)_45+x]·6MeCN (x = 0.72), which contain [H₂Ni₄₄C₈(CO)₄₆]^6? (72%) and [H₂Ni₄₃C₈(CO)₄₅]^6? (28%), have been obtained. Despite the different charges and compositions, these anions display almost identical structures, which are also closely related to those previously reported for the bimetallic Ni–Cd octa-carbido clusters [Ni_42+xC₈(CO)_44+x(CdCl)]^7? and [HNi_42+xC₈(CO)_44+x(CdBr)]^6?. Indeed, all these clusters are based on the same Ni₄₂C₈ cage decorated by miscellaneous [CdX]⁺ (X = Cl, Br), [CuCl] and [Ni(CO)] fragments.     

Energy-weighted M1 sum rule with explicit δ degrees of freedom

The influence of Δ degrees of freedom on the energy-weighted M1 sum rule is investigated and applied to ²H and ⁴He. Using π- and ρ-exchange potentials a reduction of the potential contribution of the order of 50% is obtained. The absolute value of the sum rule is strongly dependent on the short-range behaviour of the nuclear wave function. Furthermore, the contribution of c.m. effects is evaluated and found to be of the order of 5–10%.     

N-Hydroxy-o-benzenedisulfonimide: A Misunderstood Selective Oxidizing Agent

N-Hydroxy-o-benzenedisulfonimide (now an easily accessible reagent) is a useful selective oxidizing agent; this is contrary to what was previously believed. The oxidation reactions of aldehydes to acids, benzyl alcohols to aldehydes, thiols to disulfides, and sulfides to sulfoxides were investigated (18 examples).     

Bimetallic Fe–Cu Carbido Carbonyl Clusters Obtained from the Reactions of [Fe<Subscript>4</Subscript>C(CO)<Subscript>12</Subscript>{Cu(MeCN)}<Subscript>2</Subscript>] with N-Donor Ligands

The reaction of [Fe₄C(CO)₁₂{Cu(MeCN)}₂] (1) with 3 equivalents of L–L (phen or Me₂phen) affords [Cu(L–L)₂][Fe₄C(CO)₁₂{Cu(L–L)}] (L–L = phen, 2; Me₂phen, 3) in good yields. These are protonated by strong acids resulting in [HFe₄C(CO)₁₂{Cu(L–L)}] (L–L = phen, 4; Me₂phen, 5). The reaction may be reversed with bases, resulting in the quaternary ammonium salts [NR₄][Fe₄C(CO)₁₂{Cu(phen)}] (6). 4 and 5 react with a slight excess of L–L resulting in the elimination of copper in the form of [Cu(L–L)₂]⁺ and formation of the previously reported [HFe₄C(CO)₁₂]^? homometallic cluster. Conversely, the reaction of 1 with a monodentate N-ligand such as quinoline, even if used in large excess, results in the substitution product [Fe₄C(CO)₁₂{Cu(quinoline)}₂] (8), which is then transformed into [Cu(Me₂phen)₂] [Fe₄C(CO)₁₂{Cu(quinoline)}] (9) after reaction with Me₂phen. By using the anionic cluster [Fe₅C(CO)₁₄{Cu(MeCN)}]^? instead of the neutral 1, only substitution has been observed by using both phen and quinoline, resulting in [Fe₅C(CO)₁₄{Cu(phen)}]^? (10) and [Fe₅C(CO)₁₄{Cu(quinoline)}]^? (11), respectively. Finally, the reaction of 1 with [Ru(tpy)(bpy)(N₄C-C₆H₄-CN)]Cl affords crystals of [Fe₄C(CO)₁₂Cu₂Cl{Ru(tpy)(bpy)(N₄C-C₆H₄-CN)}] (12). All compounds 2-12 have been characterized by a combination of spectroscopic (IR, NMR) and crystallographic methods. All these clusters may be viewed as composed by a butterfly [Fe₄C(CO)₁₂]^2? core bonded to Cu(I) fragments and/or H⁺ ions.