Virtual coupling potential for elastic scattering of Be on proton and carbon targets

The ^10,11Be(p, p) and (¹²C, ¹²C) reactions were analyzed to determine the influence of the weak binding energies of exotic nuclei on their interaction potential. The elastic cross sections were measured at GANIL in inverse kinematics using radioactive ^10,11Be beams produced at energies of 39.1A   and 38.4A MeV$38.4A\text{ MeV}$. The elastic proton scattering data were analyzed within the framework of the microscopic Jeukenne–Lejeune–Mahaux (JLM) nucleon–nucleus potential. The angular distributions are found to be best reproduced by reducing the real part of the microscopic optical potential, as a consequence of the coupling to the continuum. These effects modify deeply the elastic potential. Including the Virtual Coupling Potential (VCP), we show the ability of the general optical potentials to reproduce the data for scattering of unstable nuclei, using realistic densities. Finally, the concepts needed to develop a more general and microscopic approach of the VCP are discussed.     

FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

Extensive new high-temperature, high-resolution FTIR emission spectroscopy measurements for the five common isotopomers of GeO are combined with previous diode laser and microwave measurements in combined isotopomer analyses. New Dunham expansion parameters and an accurate analytical potential energy function are determined for the ground X1Sigma+ state. Copyright 1999 Academic Press.     

Catalytic reactions of chlorofluoroethanes at fluorinated alumina and chromia aerogels and xerogels: A comparison of reaction pathways in alumina- and chromia-based catalysts

The differences in the dynamic behaviour of 1,1,2-trichlorotrifluoroethane over fluorinated alumina or chromia catalysts at moderate temperatures are significant. Alumina-based catalysts favour the isomerization of CCl₂FCClF₂ followed by the dismutation of CCl₃CF₃ so formed. Fluorinated chromias are less selective since halogen exchange and isomerization reactions both occur. An explanation in terms of the differences in Al---X, X=Cl or F, bond energies compared with their Cr---X counterparts is suggested. The identity of the catalyst precursor has little effect in the chromium case and no effect in the case of aluminium.     

Redox reactions involving rhenium and uranium hexafluorides,a convenient synthesis of β-uranium pentafluoride

Rhenium and uranium hexafluorides oxidise elemental iodine in iodine pentafluoride at ambient temperature to give the I₂⁺ cation. With UF₆ an additional reaction occurs to give β-uranium pentafluoride as one product, β-UF₅ is soluble in acetonitrile without disproportionation and is also formed from the reduction of UF₆ by MeCN. Copper, cadmium, and thallium metals are oxidised by ReF₆ in MeCN giving Cu^I, Cd^II, and Tl^I hexafluororhenates(V) but the reactions are complicated by reaction between ReF₆ and the solvent.     

Reactions of coordinated trimethylphosphite with binary fluorides

Fluorination of free trimethylphosphite by phosphorus pentafluoride or tungsten hexafluoride involves complex formation followed by rapid F-for-OCH₃ exchange and Michaelis-Arbusov rearrangement reactions (D.W.A. Sharp et al., $\text{J. Chem. Soc. A}$, 1969, 872; J.M. Winfield et al., $\text{ibid}$, 1970, 501). Reactions between WF₆ or PF₅ and P(OCH₃)₃, coordinated to Fe^II (low spin d⁶-inert) or Cu^I (d¹⁰ -labile) cations in CH₃CN, counter anions PF₆^? or AsF₆^?, are very different as evidenced by an n.m.r. study.Reactions between Fe^IIP(OCH₃)₃ and WF₆ are very slow at room temperature; the major products are CH₃PF₄ and WOF₄.NCCH₃. Reactions between Cu^IP(OCH₃)₃ and WF₆ or PF₅ are rapid, even below room temperature, and depend on the stoicheiometry. The major products are W₂O₂F₉^? and a PF₅X^? species, or OPF₃, minor products include CH₃OPF₂, (CH₃O)₂PF, and PF₃. When the mole ratio coordinated P(OCH₃)₃:WF₆ is 1:1, additional W₂O₂F₉ and PF₅X n.m.r. signals are observed.The reactions involve fluorination of free P(OCH₃)₃ whose concentration in solution is limited by the metal cation, and in the reaction between PF₅ and Cu^IP(OCH₃)₃ PF₅.P(OCH₃)₃ has been identified as the initial product. Conventional Michaelis-Arbusov rearrangements are of minor importance as CH₃CN acts as a sink for CH₃⁺, but the final step in the formation of CH₃PF₄ is of this type.