The First Synthesis of Organic Diselenolates: Application to the Synthesis of Diorganyl Diselenides

The addition of elemental selenium to organolithium compounds 1 or organic selenates 2 gives organic diselenolates 3 . The reactions proceed by the insertion of two selenium atoms into the carbon–metal bonds or of one selenium atom into a selenolate. Evidence for the existence of n-butyldisilenol has also been obtained.     

Slow proton andΔ ++ production inK + p interactions at 70 GeV/c

The inclusive inelastic processesK ⁺ p→pX ⁺ andK ⁺ p→Δ ⁺⁺ X ⁰ are studied at an incident momentum of 70 GeV/c. The data comes from the Big European Bubble Chamber BEBC filled with hydrogen, exposed to an rf reparatedK ⁺ beam at the CERN SPS accelerator. The inclusive cross section for protons with laboratory momentump _LAB≦1.2 GeV/c is equal to (6.1±0.1) mb. InclusiveΔ ⁺⁺-production is studied for |t _{p, Δ}|<1.0(GeV/c)². Comparisons are made with otherK ⁺ p data and withpp data at 69 GeV/c. Evidence is found for Pomeron exchange at the beam vertex both for slow proton andΔ ⁺⁺-production as well as for absorptive pion exchange at the (p,Δ ⁺⁺) vertex.     

Charged pion production in 32GeV/c K + p interactions

Final data on topological cross sections are presented. Inclusive single particle distributions for the reactionsK ⁺ p→ π^± X at 32 GeV/c are discussed and compared with data at lower energies. Early scaling in the fragmentation regions is confirmed, while cross sections in th central region continue to rise with energy even faster than inpp interactions. Thex-andp _T -dependence of the π⁺/π^? ratio inK ⁺ p interactions is discussed and a comparison of reactionsK ⁺ p→ π^± X andK ^? p→ π^± X at 32 GeV/c is made in the context of constituent models. We also present transverse momentum distributions, show prominent seagull effects and study how they are influenced by resonance production.     

Fusion excitation functions near and below the Coulomb barrier for symmetric and asymmetric medium-mass systems

Fusion excitation functions for the systems ¹²C + ^{46, 48, 50}Ti, ^{28, 30}Si + ³⁰Si and ¹⁸O + ⁴⁴Ca have been determined at energies near and below the Coulomb barrier. Inelastic excitation functions for the targets ^{48, 50}Ti and ⁴⁴Ca have been also measured in the same energy range. The absolute cross sections were obtained by in-beam γ-ray spectroscopy technique using a rotating target. Fusion cross sections ranging in magnitude from ～ 0.3 mb to ～ 1300 mb were determined with an accuracy of 10–20%. The fusion excitation functions are analysed in the frame of a semiclassical barrier-penetration model. From the analysis, the height, the radius and the curvature of the fusion barrier for the different systems are extracted. The fusion cross sections are compared with the calculations performed using different heavy-ion potentials. The enhancement of the cross sections at sub-Coulomb energies can be reproduced with a one-dimensional barrier-penetration model taking into account the zero-point motion of the surface of the reaction partners. The fusion cross section of the system ¹⁸O + ⁴⁴Ca is well reproduced by quantum-mechanical calculations, introducing a new degree of freedom taking into account the formation of a neck during the fusion process.     

Zeeman coherence in saturated absorption

By modulating the saturating beam polarization, it is possible to extract from the probe beam a signal which depends only on the Zeeman coherence Δm = 2 (transverse alignment), and to study velocity changing collisions which do not destroy the alignment. This type of collisions appears to be of small importance in neon, so that width of the saturated absorption curve from alignment is narrower than that from populations.     

Mean lifetimes of excited levels of Ar II. I. Time correlation measurements

Mean Lifetimes of excited levels of Ar II have been measured using the method of time-correlated photons in cascade. The following results were obtained: for 4p⁴S^°_{$\text{3}\text{2}$}, τ = 7·2±0·3ns; for 4p′²F^°_{$\text{7}\text{2}$}, τ = 8·8±0·2 ns; for 4p′²F^°_{$\text{5}\text{2}$}, τ = 8·0±0·2 ns. These results are compared with experimental and theoretical values.