Multiplicity structure of inclusive diffraction in À+ p andK + p interactions at 250 GeV/c

Results on the multiplicity structure of diffractively excited meson and proton systems in À⁺/K⁺ p interactions at 250 GeV/c are presented for diffractive masses up to about 9 GeV. The energy dependence of the average charge multiplicity and the shape of the multiplicity distribution in terms of KNO-scaling and negative binomial distribution are investigated. The diffractive systems are compared toe ⁺ e ^–,lh and non-diffractivehh final states as suggested by modern approaches of the Pomeron-hadron collision. Systematic differences are found between diffractive meson and proton systems but also between diffraction and the reactions compared to.     

Collinear acoustooptical interaction in annealed proton-exchanged LiNbO_3 waveguides

The performances of the proto-exchanged(PE) LiNbO_3 waveguides as a key ele-ment of acoustooptical deflector or spectrum analyzer were distinctly improved after anneal-ing.In this paper,reasons for the improvement are analysed by applying the theories of modecoupling and multilayer waveguides,so as to provide a theoretical basis for further improve-ment of the performances of the devices.     

Mössbauer effect of iron-57 intercalated in layered compound 2H−Fe0.5TaSe2

⁵⁷Fe Mössbauer effect study has been performed on intercalated compound 2H?Fe_0.5TaSe₂ over a temperature range between 14K and 500K. The highly concentrated intercalation samples 2H?Fe_xTaSe₂ with Fe atoms (x up to 2) are prepared by the electrochemical method for the first time. The Mössbauer measurement shows that iron is in Fe³⁺ high spin state and with the same probability occupies both octahedral and tetrahedral interstices of the Van der Waals gap. The fact that effective masses of iron ions in both sites are close to 57 amu and characteristic temperatures (Θ_M =130K, 107K respectively) are found to be relatively small is attributed to the weak forces on Fe³⁺.     

傅里叶自重卷积解谱技术中一种新的变迹函数

傅里叶自重卷积解谱技术可以有效地提高实验谱的分辨率,然而解谱后的信噪比明显下降。本文提出一种新的变迹函数(动态变迹函数),它可以在提高分辨率的同时使信噪比基本保持不变,用它来处理由软X射线弯品谱仪得到的Fe的Lα和Lβ实验谱线获得了十分满意的结果,解谱后得到了Lα和Lβ之间的许多短波伴线,跟理论计算值符合很符合。     

119Sn and121Sb Mössbauer studies of BaSn1−x Sb x O3 Perovskite system

The relations between the electrical characteristics of BaSn_1?x Sb _x O₃ perovskite system and the contents of BaO, Sb₂O₃ and silicate sintering agent were studied by X-ray diffraction analysis and Mössbauer spectroscopy. It was found that the electrical conductivity is related to the substitution of Sb³⁺ for Sn⁴⁺, the content of sintering agent and the phase constitutents in samples. BaSnO₃, Ba₃Sn₂O₇, Ba₂SnO₄ and SnO₂ phases might appear in different fractions when the contents of BaO change from 0.5 mole to 3.5 mole. In low antimony percentage condition, pentavalent Sb³⁺ ions inserted in Sn⁴⁺ sites and formed the donor center. In high antimony percentage (x≥0.20) condition, the existence of an insulating phase (BaSb₂O₆) was confirmed.     

Dipolar 31P NMR spectroscopy of crystalline inorganic phosphorus compounds.

The ability of the 90 degrees-t1-180 degrees pulse sequence to produce accurate dipole-dipole coupling information in solids is investigated. To this end, the experimental 31P spin echo decays are measured for eighteen crystalline phosphides and phosphorus chalcogenides and compared with simulations, based on the known internuclear distances in these compounds. The experimental results are generally found accurate in compounds where the dominant contribution to the dipole-dipole coupling arises from nuclei in structurally inequivalent sites with large chemical shift anisotropies. For this situation, the quantum mechanical "flip-flop" term in the dipolar Hamiltonian is suppressed and the dipole-dipole coupling is entirely heteronuclear in character. All of those compounds that do not obey this condition show accelerated spin echo decays due to a fractional contribution of the flip-flop term and possibly incomplete refocusing of chemical shift terms on the time scale of the experiment. The results confirm on an empirical basis that the spin echo NMR technique can provide accurate dipole-dipole coupling information (and thus distance distributions) in disordered solids and glasses.     

A simple method for measuring local buckling of thin plates

A simple computer-interfaced optical system for measuring the dynamic-local-buckling deformation of thin-walled metal structural-plate elements is described in this paper with two sets of experimental results. The major advantage of this system is its simplicity and economy as well as its speedy automated process for data scanning, acquisition, and analyses by using a microcomputer.Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics held in New Orleans, LA on June 8–13.     

Relationship between experimental pKa values in aqueous solution and a gas phase bond length in bicyclo[2.2.2]octane and cubane carboxylic acids

Linear correlations were established between the calculated bond lengths and the pK_a or σ_I values for a series of 4‐substituted bicyclo[2.2.2]octane‐1‐carboxylic acid and 4‐cubane‐1‐carboxylic acid derivatives. The bond lengths have been calculated at a modest computational level, HF/6‐31G(d), both in the gas phase and with the continuum solvation model, polarisable continuum model (PCM). In general, the best correlations are obtained when the PCM model is taken into account, especially when neutral and charged molecules are considered together. The best models in each case show square correlation coefficients (R²) larger than 0.9 and indicate that they can be used as predictive tools. These results expand previous results that indicate the possibility of a relationship between gas phase bond length and pK_a values in aqueous solution and indicate that such relationships are more general than hitherto expected. Copyright © 2013 John Wiley & Sons, Ltd.     

Pressure-induced structural transformations,orbital order and antiferromagnetism in La<Subscript>0.75</Subscript>Ca<Subscript>0.25</Subscript>MnO<Subscript>3</Subscript>

High pressure evolution of structural, vibrational and magnetic properties of La_0.75Ca_0.25MnO₃ was studied by means of X-ray diffraction and Raman spectroscopy up to 39 GPa, and neutron diffraction up to 7.5 GPa. The stability of different magnetic ground states, orbital configurations and structural modifications were investigated by LDA + U electronic structure calculations. A change of octahedral tilts corresponding to the transformation of orthorhombic crystal structure from the Pnma symmetry to the Immaone occurs above P ~ 6 GPa. At the same time, the evolution of the orthorhombic lattice distortion evidences an appearance of the e _g d _{x² ? z²} orbital polarization at high pressures. The magnetic order in La_0.75Ca_0.25MnO₃ undergoes a continuous transition from the ferromagnetic 3D metallic (FM) ground state to the A-type antiferromagnetic (AFM) state of assumedly 2D pseudo-metallic character under pressure, that starts at about 1 GPa and extends possibly to 20–30 GPa.