Final state interactions in deuteron breakup by protons at 585 and 800 MeV

Neutron-proton final state interactions (FSI) were observed in the deuteron breakup reaction ²H(p, 2p)n-via a kinematically complete experiment at incident proton energies of 585 and 800 MeV. Kinematic conditions were chosen which allowed the final state proton and neutron to have small relative energies; data were taken at four proton c.m. scattering angles at 800 MeV, ranging from 71° to 119° and at 94° and 106° at 585 MeV. The data are analyzed in terms of the Goldberger-Watson formalism for final state interactions, and the individual contributions of the ¹S₀ and ³S₁ np states are determined. The ${}^3\text{S}{}_1{}^1\text{S}{}_0$ ratio is large, as expected from some reaction models. The ratio of ³S₁ (almost elastic) to pd elastic cross sections is in good agreement with FSI analysis.     

Raman spectrographic system for quantitative analysis of isotopic hydrogen mixtures for muon catalysis experiments

We show that Raman spectral lines from H₂, D₂, T₂, HD, HT and DT are readily resolved, permitting an effective means to analyze isotopic hydrogen mixtures used in muon-catalyzed fusion experiments. We propose a Raman spectrographic system to allow for real-time analysis of targets involving all three isotopes of hydrogen.     

Measurements of 12C(π+, πN)11C and 19F(π+, πN)18F cross sections near the 32, 32 resonance

Reaction cross sections for ¹²C(π⁺, πN)¹¹C at 134, 161, 177, and 200 MeV and for ¹⁹F(π⁺,πN) at 161, 177, and 200 MeV were measured by activation methods.     

Spectroscopic studies of the conformations of n-decamethyltetrasilane

The conformational properties of n-decamethyltetrasilane, n-Si₄(CH₃)₁₀, have been studied by variable temperature NMR (¹H and ¹³C) and vibrational (IR and Raman) spectroscopy. As in related alkane systems, the anti conformer ismore stable than the gauche conformer. Values of △H⁰ and △S⁰ for the anti → gauche reaction are 2.26 ± 0.15 kJ mol^-1 and △S⁰ = 7.82± 0.86 J K^-1mol^-1, respectively. Thus, the two conformers are present in comparable quantities at room temperature. At very low temperatures, broadening of the two proton resonances (SiMe₂, SiMe₃) occurs, but phase changes precluded the observation of decoalescence. By approximate lineshape anaylysis, the free energy of activation, △G3, for rotation about the central SiSi bond is estimated to be ～25 kJ mol^-1.     

Pion small-angle multiple scattering at energies spanning the (3,3) resonance

The small-angle multiple scattering of positive and negative pions has been measured for C, Al, Cu and Pb targets throughout an energy range spanning the (3, 3) resonance. The measurements were made using two-dimensional multiwire proportional counters placed in the pion beam. All previous multiple scattering data for electrons and protons as well as these new data for pions are used to recalculate the empirical terms in the Moliere theory of multiple scattering. A second-order Born approximation multiple scattering theory has been devised for spin zero particles. Modified Moliere theory gives a better fit to the experimental data than the second-order Born calculation. Because the updated Moliere theory contains much simpler equations and gives closer agreement with experiment, it is recommended in place of the more sophisticated theory for the interpretation of new experimental data.     

Enantioselective Total Synthesis of Macfarlandin C,a Spongian Diterpenoid Harboring a Concave-Substituted cis-Dioxabicyclo[3.3.0]octanone Fragment

The enantioselective total synthesis of the rearranged spongian diterpenoid (−)-macfarlandin C is reported. This is the first synthesis of a rearranged spongian diterpenoid in which the bulky hydrocarbon fragment is joined via a quaternary carbon to the highly hindered concave face of the cis-2,8-dioxabicyclo[3.3.0]octan-3-one moiety. The strategy involves a late-stage fragment coupling between a tertiary carbon radical and an electrophilic butenolide resulting in the stereoselective formation of vicinal quaternary and tertiary stereocenters. A stereoselective Mukaiyama hydration that orients a pendant carboxymethyl side chain cis to the bulky octahydronapthalene substituent was pivotal in fashioning the challenging concave-substituted cis-dioxabicyclo[3.3.0]octanone fragment.