Surface alpha-clustering in the lead region

The effect of shell model configuration mixing on the reduced α-amplitude in heavy nuclei is investigated and discussed with respect to the question of α-clustering in nuclei. It is shown that extensive configuration mixing may enhance the α-amplitude under the Coulomb barrier by huge, largely arbitrary factors. In contrast to this the actual αclustering in the nuclear surface may well be described within the shell model including only relatively few configurations in the open shell.     

Parallel susceptibility of chain-like antiferromagnets

The parallel susceptibility of chain-like antiferromagnets is obtained by the spin wave theory considering kinematical interaction. The result obtained is very similar to that given by the Green function method for usual antiferromagnets. The correction due to kinematical interaction is expressed as a function of the spin reduction. It is found that the effect of kinematical interaction on the susceptibility is very large for chain-like antiferromagnets. Dynamical interaction is shown to contribute also greatly to the susceptibility. Numerical calculations are made for KCuF₃. Case of antiferromagnetic and ferromagnetic inter-chain exchange interaction are investigated numerically and it is concluded that the sign of the inter-chain exchange interaction is not important for chain-like antiferromagnets.     

Triangle contraction in six-membered-ring silicon clusters

We propose the “triangle contraction” as an important reconstruction mechanism of six-membered-ring silicon clusters on the basis of the force and virial analysis for Si₆, Si₁₀, Si₁₄, Si₁₈, Si₂₂, and Si₂₆ clusters. Forces acting on atoms have been calculated using the local-density-functional scheme with linear-combination-of-atomic-orbitals-Xα method. Calculated forces show that most of the (111)-surface equilateral triangles have tendency to contract, indicating the generality of the triangle-contraction mechanism.     

Laser photolysis of C2H2 and CF3C2H at 193 nm: Production of C2(d3Πg and CH(A2Δ) and their quenching by Xe

The 193 nm laser photodissociation of CH₂H₂ and CF₃C₂H has been studied. With the laser beam focused, C₂(d³Π_g) and CH(A²Δ) radicals were formed by multiphoton processes in both C₂H₂ and CF₃C₂H; however, the one-photon process forming C₂H is still predominant in CF₃C₂H photolysis. The production of C₂(d³Π_g) and CH(A²Δ) emissions is prompt,and the emission intensities show similar (less than quadratic) dependence on laser power whether the radicals are produced from C₂H₂ or CF₃C₂H. In addition, the vibrational distribution of the Swan system is nearly the same in CF₃C₂H as in C₂H₂. The results indicate that the overall photolytic processes are similar in two molecules. Both the C₂(d³Π_g) and CH(A²Δ) emissions are quenched by Xe with rate constants of 4.8×10^?11 and 1.8×10^?11 cm³ molecule^?1 s^?1, respectively.     

Studies on sesquiterpenoids—III Some derivatives of guaiol

When guaiol was dehydrated with such reagents as thionyl chloride-pyridine, phosphorus oxychloride-pyridine or potassium bisulphate, the isopropenyl derivative (IIa) was always obtained as a main product, together with a small amount of IIb. Catalytic reduction of IIa in alkaline media afforded -dihydroguaiene (V), while in neutral or acid media it gave a mixture of V and its double bond isomer (VI).     

Susceptibility of low-dimensional antiferromagnets

The effect of kinematical interaction in the spin-wave theory on the perpendicular susceptibility of quadratic and chain-like antiferromagnets is examined. Results obtained for the perpendicular susceptibility of quadratic antiferromagnets agree with the experimental values at absolute zero for all spin quantum numbers. Numerical calculation of the perpendicular susceptibility of KCuF₃ is made and a large deviation from that due to the simple spin-wave theory is found, as was noted previously for the magnetization.