Study of the reactione + e −→K + K − in the energy range1350 \leqq \sqrt s \leqq 2400 MeV

Thee ⁺ e ^?→K ⁺ K ^? cross section has been measured from about 750 events in the energy interval \(1350 \leqq \sqrt s \leqq 2400 MeV\) with the DM2 detector at DCI. TheK ^± form factor |F _F ^±| cannot be explained by the ρ, ω, ? and ρ′(1600). An additional resonant amplitude at 1650 MeV has to be added as suggested by a previous experiment.     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

Non-planar smoulder propagation governed by diffusion

The steady propagation of a thin smouldering front in a half-spacehas been considered. A suitable coordinate transformation hasallowed the region near the leading edge of the front to beexamined for both a maintained planar surface and with surfacecollapse due to material shrinkage. The change in the oxidizerconcentration for a small increment in the propagation speedfor large time and surface collapse has been determined. Theinfluence of two types of nonlinear diffusion on the shape ofthe smouldering front has been found; other cases can be dealtwith in a similar manner.     

Coordination chemistry of 1,4-bis-carboxymethylcyclam, H(2)(1,4-bcc)

Zinc metal reduction of the cobalt(III) complex [Co(1,4-bcc)](+) (1,4-bcc = 1,4-bis-carboxymethylcyclam) produces the corresponding cobalt(II) complex which crystallises as the coordination polymer {[Co(1,4-bcc)]ZnCl(2)}(n). A method has been developed for removal of the cobalt(III) ion from [Co(1,4-bcc)](+) and isolation of the free ligand as its hydrochloride salt, H(2)(1,4-bcc).4HCl. This has been used for the preparation of new metal complexes, and the syntheses and characterisation of the copper(ii), nickel(ii), zinc(ii) and chromium(iii) complexes containing the 1,4-bcc ligand are described. X-Ray crystal structures of {[Co(1,4-bcc)]ZnCl(2)}(n).2.5H(2)O, {[Cu(1,4-bcc)]CuCl(2)}(n).0.25MeOH.H(2)O and [Cu(1,4-bcc)H]ClO(4) show the complexes to have the trans(O) geometry of the 1,4-bcc ligand, while the structure of [Cr(1,4-bcc)H(0.5)](ClO(4))(1.5).EtOH exhibits the cis(O) configuration.     

KMgF3:Ni2+晶体的占位、局部结构、吸收光谱和顺磁g因子的统一解释

利用完全对角化方法和强场耦合方案,采用半自洽场(semi-SCF)自由Ni2+的d轨道模型和Ni2+-6X-(x=F,Cl,Br,I)络合物的μ-κ-α模型研究,建立了含有过渡族金属离子的晶体的局域结构与吸收光谱和顺磁g因子之间的定量关系,对KMgF3:Ni2+晶体的占位、局域结构、吸收光谱和顺磁g因子作出了统一解释,预测了KMgF3:Ni2+晶体的光谱精细结构.所得理论计算结果与实验值符合得很好.     

C-H Activation of 3,3-diphenylcyclopropene in the reaction with Os(CO)2(PPh3)3: 3,3-diphenylcyclopropenyl, 2,2-diphenylcyclopropyl, and 3-phenylindenyl complexes of osmium(II)

Reaction between Os(CO)₂(PPh₃)₃ and 3,3-diphenylcyclopropene under quartz-halogen irradiation leads to C(sp²)-H bond activation and the formation of the 3,3-diphenylcyclopropenyl complex, OsH[C₃H(Ph-2)₂](CO)₂(PPh₃)₂ (1). When complex 1 is heated there is ring-opening of the cyclopropene ring and rearrangement to the 3-phenylindenyl complex, OsH[C₉H₆(Ph-3)](CO)₂(PPh₃)₂ (2). Compound 1 reacts with HCl forming the 2,2-diphenylcyclopropyl complex, OsCl[C₃H₃(Ph-2)₂](CO)₂(PPh₃)₂ (3). Reaction of either 1 or 3 with excess HCl leads to reversible formation of the hydroxycarbene complex, OsCl₂[C(OH)C₃H₃(Ph-2)₂](CO)(PPh₃)₂ (4), through protonation of the acyl group formed by a migratory insertion reaction involving a carbonyl ligand and the σ-bound 2,2-diphenylcyclopropanyl ligand. An X-ray crystal structure determination of 2 is reported.     

Baryon pairs production ine + e − annihilation at\sqrt s = 2.4 GeV

Search for baryon pairs production ine ⁺ e ^? annihilation at \(\sqrt s = 2386 MeV\) is reported. The data relate to a luminosity of 161 nb^?1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe ⁺ e ^? annihilation into \(\Lambda \bar \Lambda \) and ofe ⁺ e ^?→ \(p\bar p\) at this energy are presented. First observation of a goode ⁺ e ^?→ \(n\bar n\) candidate is reported and upper limits are given fore ⁺ e ^?→ \(n\bar n, \Lambda \bar \sum ^0 + c.c.\) and \(\Sigma ^0 \bar \Sigma ^0 \) .     

Synthesis and characterization of a new class of polyfluorinated alkanes: tetrakis(perfluoroalkyl)alkane

The synthesis and physico-chemical characterization of 1,1,2,2-tetrakis(perfluoroalkyl-methylene)ethane {[F(CF₂)_nCH₂]₂CH}₂ (n=6, TK6; n=8, TK8) are reported. The synthesis consists of four steps: (1) addition of allyl alcohol to a perfluoroalkyl iodide, F(CF₂)_nI (n=6,8) to give the corresponding iodo-adduct; (2) dehalogenation of the adduct by treatment with zinc in aqueous acetic acid, yielding 3-perfluoro-n-alkyl-1-propene; (3) addition of 3-perfluoro-n-alkyl-l-propene to perfluoroalkyl iodide, F(CF₂)_nI (n=6,8) to give 1,3-perfluoro-n-alkyl-2-iodo-propane; (4) coupling of 1,3-perfluoro-n-alkyl-2-iodo-propane by zinc in acetic anhydride giving the final products. TK6 and TK8 are characterized by very low surface tension values and exhibit very good properties as potential ski-waxes.