Measurement of the branching fraction of Gamma(4S) --> B0B0

We report the first measurement of the branching fraction f(00) for Gamma(4S) --> B(0)B(0). The data sample consists of 81.7 fb(-1) collected at the Gamma(4S) resonance with the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring. Using partial reconstruction of the decay B(0) --> D(*+) l(-)nu(l) in which only the charged lepton and the soft pion from the decay D(*+) --> D(0)pi(+) are reconstructed, we obtain f(00) = 0.487 +/- 0.010(stat) +/- 0.008(syst). Our result does not depend on the branching fractions of B(0) --> D(*+)l(-)nu(l) and D(*+) --> D(0)pi(+) decays, on the ratio of the charged and neutral B meson lifetimes, nor on the assumption of isospin symmetry.     

The structures of [C4H4]+˙ ions by photodissociation in an ion cyclotron resonance spectrometer

The photodissociation of [C₄H₄]⁺˙ fragment ions at the ion cyclotron resonance time-scale competes with relaxation of the internal energy by infrared emission. As a result the fraction of photodissociating ions increases with light intensity. The experiments indicate that [C₄H₄]⁺˙ from benzene and 1,5-hexadiyne consists of a mixture of 60% vinyl acetylene ions, 10% butatriene ions and 30% cyclic ions. This confirms previous conclusions from studies of the ion-molecule reactions of [C₄H₄]⁺˙ with benzene.     

The structures of some cycloalkane molecular ions by photodissociation and charge-transfer studies in an ICR-spectrometer

The photodissociation spectra of the molecular ions of some cycloalkanes are compared with those of the corresponding acyclic alkanes and alkenes. It is shown that the molecular ions of cyclohexane and cycloheptane are cyclic whereas the cyclopentane ring opens upon ionisation. This conclusion is supported by a study of the charge-transfer equilibria: C₆D₁₂^± + C₆H₁₂ ? C₆D₁₂ + C₆H₁₂^±, C₅D₁₀^± + C₅H₁₀ ? C₅D₁₀ + C₅H₁₀^±. It is furthermore shown that the maxima in the photodissociation spectra of the molecular ions of saturated hydrocarbons correspond to different dissociation processes.     

Diamino-benzo[1,2-d:4,5-d′]bistriazole (DABT), a new useful 1,4-dibenzyne equivalent

The title compound, when treated with two equivalents of lead tetraacetate, is the synthetic equivalent of 1,4-dibenzyne; bis-cycloadducts are formed with dienes and 1,3-dipoles.     

The formation and molecular structure of acetylcyclopentadienylsodium-tetrahydrofuranate

Acetylcyclopentadienylsodium has been isolated in crystalline form as a THF adduct from a reaction between cyclopentadienylsodium and methyl acetate in THF solution. The product has been characterized by means of a single-crystal X-ray diffraction study. {[C₅H₄CMeO]Na·THF}_n crystallizes in the monoclinic space group P2₁/c with unit cell parameters a 6.698(3), b 16.095(4), c 10.661(3) Å, β 92.93(3)° and D_c 1.17 g cm^?3 for Z = 4. Least-squares refinement led to a final R value of 0.080 based on 661 independent observed reflections. The coordination sphere around each sodium atom consists of the oxygen atoms from two C₅H₄CMeO ligands, the oxygen atom of the THF molecule, and an ion contact pair between the sodium and the five ring carbon atoms of the C₅H₄CMeO ligand.     

Spin-rotation measurements in π−p → K0Λ

The first measurements of spin-rotation in meson-baryon scattering in the resonance region are presented. These measurements, for the reaction π^?p → K⁰Λ, confirm the main predictions of a previous partial-wave analysis. Comments are made on resonant couplings in the reaction π^?p → K⁰Λ.